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The unique predatory, caching, and impaling behaviors of shrikes (Laniidae) may provide these unusual passerines with alternative provisioning strategies compared to other songbirds, but few studies have determined the impact these unique behaviors have on provisioning rates. Our objectives were to compare the provisioning behavior of male and female Loggerhead Shrikes ( Lanius ludovicianus), and determine how their provisioning behavior was influenced by nestling age. The provisioning behavior of six pairs of Loggerhead Shrikes was videotaped from 15 April to 15 August 2004–2007 in Garrard and Madison counties, Kentucky, USA. For each nest visit by a shrike, the sex of the visiting adult, number of prey items delivered, size of prey, type of prey, and the duration of the nest visit were recorded. Adults made 2169 visits to nests, with males (49%) and females (51%) making similar numbers of visits. Males and females differed in time spent at nests, with males spending less time at nests per visit (mean = 12.0 s, N = 1062) than females (77.0 s, N = 1107). Feeding rates did not differ between the sexes, but feeding rates did increase with nestling age. The size of prey delivered to nestlings also tended to increase with nestling age. Invertebrates comprised 65% of the identified prey items, and cached items made up the remaining 35%. Although many passerine species increase provisioning rates as nestling demand increases, the caching behavior of shrikes may allow adults to reliably increase both feeding rates and prey size as nestling age and demand increase as well as act as buffers when prey availability declines. The caching behavior of shrikes provides them with parental provisioning strategies not available to non-caching songbirds.

Most species of songbirds exhibit biparental care, but, for many taxa and species, little is known about the relative contributions of males and females in brooding and provisioning nestlings. Additional studies of the contributions of males and females in brooding and feeding nestlings are needed to better understand the respective roles of males and females as well as the factors that might contribute to interspecific variation in those roles. We examined the roles of adult male and female White-eyed Vireos ( Vireo griseus) in brooding and provisioning nestlings in east-central Kentucky during the 1996 breeding season. Nests were located by monitoring adult behavior and checking likely nest sites. Once eggs hatched, nests were video-recorded to monitor the behavior of adults. Subsequent review of videos revealed that both male and female White-eyed Vireos brooded young and that males provisioned nestlings at higher rates than females. In contrast to males in many other species of songbirds, male White-eyed Vireos assisted in brooding young and provisioned nestlings at higher rates than their mates. One possible explanation for this is that low rates of extra-pair paternity might increase male confidence of their paternity status. Parental care provided by male White-eyed Vireos may also limit energy expenditure by their mates and increase the likelihood of females re-nesting if nests are predated or initiating second nesting attempts if initial attempts are successful.

When perched, several species of small falcons, including American Kestrels (Falco sparverius), often pump their tails, but the possible function of this behaviour is unknown. Our objective was to use observations and experiments to examine the possible function(s) of tail-pumping by American Kestrels. Fieldwork was conducted from March 2015 to December 2015 at the Blue Grass Army Depot in Madison County, Kentucky. During observations of focal kestrels, we noted their behaviour (e.g. landing on a perch, hunting, or consuming prey), including when and how often they pumped their tails (i.e. rapid movement of the tail down, then back up to its original position). Kestrels typically tail-pumped when landing on a perch (mean = 4.1±0.2 pumps per 10 s) and consuming prey (mean = 2.4±0.2 pumps per 10 s). When hunting, kestrels tail-pumped at higher rates during the 30 s prior to attacking (mean = 1.1±0.3 pumps) than they did during the 30–60 s interval before an attack (mean = 0.3±0.1 pumps). During experiments where kestrels were presented with models of a conspecific and a predator (Cooper's Hawk, Accipiter cooperi), we found no difference in rates of tail-pumping prior to and during the presentation. These results suggest that tail-pumping by American Kestrels is not used either to communicate with conspecifics or as a predator-deterrent signal. Rather, kestrels appear to tail-pump to help maintain balance on perches when landing and consuming prey. In addition, prior to attacking prey, kestrels typically bob their heads (possibly to aid in judging distances), and tail-pumping may help them maintain stability as they head-bob and prepare to attack.

Some species of birds use their vocalisations to communicate predator presence and the level of threat they pose, including two species of corvids (Corvidae), American Crows (Corvus brachyrhynchos) and Siberian Jays (Perisoreus infaustus). Our objective was to determine if Blue Jays (Cyanocitta cristata), another corvid, also use specific calls or vary the characteristics of certain calls to convey information about the level of threat posed by aerial predators. During the non-breeding seasons of 2014 and 2015, we recorded and analysed the vocal responses of Blue Jays to study skins of six species of raptors that varied in size and the level of threat they pose to Blue Jays. Experiments were conducted at seven locations in Madison County, Kentucky. The mean number of Blue Jays present during trials was 2.6, and Blue Jays uttered five different vocalisations during trials, with ditonal and monotonal jeers given most frequently. The rate at which Blue Jays uttered ditonal jeers differed among trials, with rates highest during trials with an Eastern Screech-Owl (Megascops asio) and a Sharp-shinned Hawk (Accipiter striatus). However, the characteristics of ditonal and monotonal jeers (duration, low frequency, high frequency, and peak frequency) did not differ among trials. These results suggest that Blue Jays may either perceive Eastern Screech-Owls and Sharp-shinned Hawks as the greatest threats or, alternatively, as potential, but less threatening predators, and, therefore, they were willing to take greater risks when mobbing them. In contrast, Blue Jays mobbed the other raptors, i.e. American Kestrels (Falco sparverius), Red-tailed Hawks (Buteo jamaicensis), and Great Horned Owls (Bubo virginianus), with much less intensity, likely because they posed less of a threat or, in the case of Cooper's Hawks (Accipiter cooperii) that are known predators of Blue Jays, perhaps because mobbing with greater intensity, e.g. approaching more closely, posed too great a risk. Blue Jays in our study used the same calls with the same characteristics when responding to potential predators, only calling rates differed. However, such variation in calling rates when mobbing would likely provide useful information about the presence of, and possibly the threat posed by, potential predators for conspecifics and, perhaps, heterospecifics.

Breeding is an energetically costly activity for birds. If energy-limited, birds may alter their time budgets, reducing time spent in some activities and spending more time in others. To date, no experimental study has investigated the possible effect of food availability on male mate guarding behavior. Additionally, previous results from food supplementation studies are mixed. My objectives were to determine how food supplementation might influence the breeding behavior of male Indigo Buntings (Passerina cyanea). I predicted that, compared to non-supplemented males, food-supplemented males would: 1) spend less time foraging, 2) spend more time singing, 3) spend more time mate guarding, 4) respond more aggressively to a simulated intruder (i.e. playback of conspecific songs in their territories), and 5) have fewer EPY in their nests. Behavioral observations were conducted at the Miller-Welch/Central Kentucky Wildlife Management Area from 8 May – 15 August 2009. Territories of male buntings (N = 30) in my study area were randomly selected for either food supplementation (n = 8) or controls (n = 22). During time budget observations (20 min/day/focal male), all behaviors were noted. To quantify male aggression, playback experiments were conducted on a subset of six food-supplemented males and six non-food-supplemented males, when numerous aggressive-like behaviors were noted. To determine paternity, blood samples were collected from adults and nestlings at 19 nests. DNA was extracted, amplified, and hand-scored on polyacrylamide gels. Males with feeders in their territories spent significantly less time foraging and significantly more time chipping than males without feeders in their territories. Time spent singing and mate guarding was not statistically different between treatment and control males. Differences in aggressive behaviors and the proportion of EPY approached significance with those males with feeders in their territories exhibiting more aggressive-like behaviors and having more EPY in their nests. Of 16 broods, 12 (75%) had at least one EPY and, in those broods, 24 of 43 nestlings (56%) were EPY. My results suggest that when provided with supplemental food, males can spend less time foraging, and in turn, will have more time and energy to devote to other activities. The presence of supplemental food however, has appeared to increase the rates of intruding, neighboring males. When neighboring conspecifics are drawn to territories with supplemental food, more EPC opportunities exist for females on supplemented territories, therefore leading to a greater proportion of EPY for those females and suggesting that female buntings are not using food as an indicator of habitat or male quality. Mate guarding did not act to fully protect paternity and regardless of time spent mate guarding, females, whether mated to food-supplemented males or not, were not guarded for the majority of the time, thereby permitting ample opportunities to seek EPCs themselves. In addition, female buntings do not risk the loss of male…

Little is known about how variation in nestling begging intensity influences the behaviour of adult raptors and how responses of adult males and females to such variation might differ. Our objective was to manipulate the begging intensity of nestling American Kestrels (Falco sparverius) and examine the responses of adults. We studied 12 pairs of American Kestrels nesting in nest boxes from 1 March to 1 July 2014 at the Blue Grass Army Depot, Madison County, Kentucky. Nest boxes were modified with a separate compartment for a camcorder to record nestling behaviour, and a second camcorder was placed outside the nests to monitor adult behaviour. To manipulate nestling hunger levels, 12 to 26-day-old nestlings in six nests were deprived of food for 24 h and those in the other six nests were fed until satiated. At each nest, we alternated control (no treatment) and treatment (fed or food deprived) days over a 4 day period to minimise the possible effect of nestling age on adult and nestling behaviour. Nestling begging intensity differed among treatments, with nestlings in food-deprived nests begging with greater intensity after food deprivation and those in fed-treatment nests begging with less intensity after being fed. Adult male and female American Kestrels provisioned nestlings at similar rates, with both sexes feeding nestlings at higher rates after food deprivation and at lower rates after fed treatments. Thus, the begging behaviour of nestling American Kestrels varied with hunger level, and adult American Kestrels responded by adjusting provisioning rates. Although the response of adults to nestling begging suggests that natural selection might favour ‘dishonest’ begging to obtain more food, the potential costs of ‘dishonest’ begging, such as attracting predators, reduced immunocompetence, and loss of indirect fitness benefits if such begging negatively impacts siblings and parents, may outweigh any possible benefit.

Although most owls exhibit biparental care, the relative contributions of males and females during critical life cycle stages are poorly understood. Further information could improve our understanding of the feeding ecology of owls and of mechanisms that govern natural and sexual selection, particularly as they relate to the evolution of reversed sexual dimorphism. The objective of our study was to assess possible intersexual differences in provisioning behavior (visit rate and prey size and type) of slightly dimorphic Eastern Screech-Owls (Megascops asio; females 17% greater mass than males) during the post-brooding period when both adults provision nestlings. Pairs of Eastern Screech-Owls provisioned young with 16 different types of prey in our study with insects and crayfish (Family Astacidae) being the most common. We found no differences between females and males in provisioning rate or in mean size of prey delivered. Our findings suggest Screech-Owls are opportunistic feeders in the post-br...

Nestling birds solicit food from their parents using conspicuous vocalizations and visual begging displays, and evidence suggests begging represents an honest signal of need that adults use to determine provisioning rates. Less is known about how adult males and females may differ in response to changes in nestling begging behavior as a result of variation in hunger levels or how nestling begging and adult provisioning may vary seasonally in multi-brooded species. To examine these parent-offspring interactions, we manipulated hunger levels of nestling Eastern Phoebes (Sayornis phoebe) during the 2011 breeding season in central Kentucky. Both first and second broods were divided into three treatments: whole brood fed (n = 12), whole brood deprived (n = 16), and some fed/some deprived (split; n = 14). Food-deprived nestlings begged with increased intensity, and fed broods begged with less intensity. Adult Eastern Phoebes adjusted their provisioning rates accordingly, provisioning food-deprive...

The alarm calls of some birds are functionally referential and may provide nestlings with information about the threat posed by potential predators. However, few investigators have examined the responses of nestlings in cavity nests to the anti-predator vocalizations of adults. Our objectives were to examine (1) the vocal responses of cavity-nesting adult Eastern Bluebirds (Sialia sialis) to different predators, and (2) the behavioral responses of nestlings to those vocalizations. From April–July 2013, pairs of Eastern Bluebirds were exposed to mounts or models of four potential nest predators, including a raccoon (Procyon lotor), eastern chipmunk (Tamias striatus), American Kestrel (Falco sparverius), and black rat snake (Pantherophis obsoletus), plus a control (Mourning Dove, Zenaida macroura). During 3-min trials, mounts or models were placed adjacent to nest boxes with 12–19-day-old nestlings. Adult vocalizations were recorded and the behavior of nestlings simultaneously recorded with a camco...

The provisioning behavior of male and female songbirds varies among species, but most species exhibit biparental care. Our objective was to examine the provisioning behavior of male and female Indigo Buntings (Passerina cyanea), a species where males are reported to provide little or no parental care. Nests (n = 16) were video-taped during the 9-day nestling period and provisioning rates of adult buntings subsequently quantified. Provisioning rates of female buntings varied with nestling age, with 7–9-day old nestlings fed at higher rates than 1–6-day old nestlings. This increase was likely because of the increasing energy demands of nestlings. Male buntings provisioned nestlings at only three of 16 nests (18.8%), and primarily on days 7–9 post- hatching. Given the apparent relationships among paternal care, mating systems, and habitat characteristics, high-quality habitat may be an important factor contributing to reduced levels of paternal care by male buntings, along with opportunistic polyg...

In species susceptible to mass-dependent flight costs, mass recession prior to fledging may ensure that fledglings have appropriate wing loading. Our objectives were to determine if mass recession by chimney swift Chaetura pelagica nestlings is intrinsically controlled or facultatively adjusted by nestlings, and if mass recession is driven by changes in parental (i.e. reduced provisioning rates) or nestling (i.e. reduced begging) behavior. Nestling swifts (n = 50 in 17 broods) were divided into three treatment groups: controls, half-weighted, or weighted. Half-weighted and weighted nestlings had 0.6–0.7 or 1.2–1.3-g lead weights, respectively, glued to body feathers on their backs during the period from 16 to 26 d post-hatching. Weighted nestlings lost more mass than control and half-weighted nestlings. After accounting for the added weights, control nestlings also had a higher wing loading than weighted nestlings. Video recordings revealed that provisioning rates of adult swifts did not vary throughout the nestling period, but the percent time nestlings spent begging increased slightly with age. Differences in mass recession among nestlings in different treatment groups resulted in convergence toward similar wing loading values likely optimal for flight efficiency. Mechanism(s) involved in this process remain unclear because provisioning rates were similar (from day 12 to 26 post-hatching) whereas percent begging time by nestlings tended to increase with nestling age. However, weighted nestlings may have lost more mass than control nestlings by soliciting less food from adults than siblings, being more active, losing more water due to tissue maturation, or through some combination of two or more of these factors.

Nestlings of some aerial insectivores experience pre-fledging mass recession, possibly to achieve optimum wing loading at fledging. However, studies to date where mass recession was linked...

Because of their cryptic plumage and nocturnal habits, little is known about the breeding behavior of Chuck-will's-widows (Antrostomus carolinensis). Using temperature loggers and video-recordings, we quantified the incubation, brooding, and provisioning behavior of male and female Chuck-will's-widows in Adams County, Ohio, in 2011 and 2012. We located six nests, all 2-egg clutches laid on the ground. Four nests were successful, one was depredated, and one was abandoned. We quantified incubation behavior at all nests (mean = 5.5 days; range = 0.4–12.9 days). Adult Chuck-will's-widows incubated an average of 89.2% of the time, with females observed incubating more than males. Most incubation off-bouts (n = 104) occurred at dawn (0400–0659; n = 45) and dusk (1900–2200; n = 48) and averaged 35 mins in duration. After hatching, the mean duration of brooding bouts was 20 mins (age of young = 1–7 days). Both males and females provisioned young, and feeding rates were highest (P = 0.003) d...

Because Sharp-shinned Hawks (Accipiter striatus) are among the most secretive of North America's forest-breeding raptors, little is known about their breeding biology, including the characteristics of their nesting habitat. In 2009 and 2010, we searched forest stands in Kentucky and located 11 nests, all in pines (Pinus spp.). Nests were at a mean height of 18.6 ± 1.4 m in trees with a mean height of 23.7 m. Comparison of the characteristics of nest sites and randomly selected unused sites revealed significant differences (P = 0.021). Discriminant analysis revealed that six variables (foliage cover, mean tree height, basal area, percent deciduous canopy cover, distance from edge, and distance from road) permitted the best discrimination between used and random sites. Sharp-shinned Hawks nested in areas closer to edges and in areas with denser stands of taller conifers and denser understory. All nests were in stands of young (∼25–50 years), even-aged conifers about 18–25 m in height. Nest sites ...

To maximize reproductive success, parents may differentially invest in sons and daughters, i.e., sex-biased parental investment. Preferential provisioning behavior has been reported in one population of Sialia sialis (Eastern Bluebird) and attributed to local resource competition. We studied the provisioning behavior of Eastern Bluebirds in Madison County, KY in 2004. We experimentally manipulated brood sex ratios in 24 bluebird nests, creating female-biased (n = 8), male-biased (n = 5), and control (n = 11) nests. Following manipulation, nests were videotaped to record adult provisioning behavior. Brood sex ratio had no effect on the provisioning behavior of either male or female Eastern Bluebirds. Similarly, we found no effect of brood sex ratio on the provisioning rates of either male or female bluebirds for control broods that naturally differed in number of male and female nestlings (n = 9; 5 male-biased and 4 female-biased). Our results contrast with those of a previous study that found t...

Tufted Titmice (Baeolophus bicolor) and Carolina Chickadees (Poecile carolinensis) often occur together in mixed species flocks during the non-breeding season and, as nuclear species, often initiate mobbing bouts. We compared the mobbing behavior of Tufted Titmice and Carolina Chickadees and, specifically, their tendency to approach five potential predators. We exposed flocks of chickadees and titmice to study skins of five species of raptors in 2008; raptors were categorized as either low-threat (rarely preying on chickadees or titmice) or high-threat (more likely to prey on chickadees or titmice). We noted the distance of closest approach by titmice and chickadees during trials, and whether a chickadee or titmouse spent more time within 5 m of the raptor. Titmice were more likely to remain within 5 m of both low (p = 0.0008) and high-threat (p = 0.0015) raptors. Titmice approached low-threat raptors closer than chickadees (p = 0.014). There was no difference in the mean distance of closes...

Staging areas along the coasts provide reliable food resources, and shorebirds may use the same stopover locations every year. However, shorebirds use sites opportunistically in the interior of North America because of the transient nature of many habitats. Little is known, however, about the use of wetlands by migrating shorebirds in many areas of the Mississippi Alluvial Valley (MAV), including Kentucky. During 2004 and 2005, we examined the phenology of migration by shorebirds using stopover habitats in Kentucky. From March to October, we surveyed shorebirds in each moist soil unit as well as at other natural and man-made wetlands at each wildlife management area. Species abundance was recorded a minimum of once every 10-day period. We observed 25 species and 12,307 individual shorebirds during our study, with Charadrius vociferous (Killdeer; n = 4134), Calidris melanotos (Pectoral Sandpiper; n = 2912), Calidris minutilla (Least Sandpiper; n = 1138), Tringa melanoleuca (Gmelin) (Greater Yellow...

We examined the provisioning behavior of male and female Grasshopper Sparrows (Ammodramus savannarum) during 2002 and 2003 by videotaping nests (n = 15) and subsequently reviewing tapes to quantify provisioning rates and identify prey items. There was no difference in provisioning rates of male and female Grasshopper Sparrows (P = 0.13) with mean rates of 2.16 visits/hr for females and 1.86 visits/hr for males. Provisioning rates for males and females combined varied with nestling age (P = 0.01) with rates lower for 1–4-day-old nestlings, increasing through day 6 and then declining for 7–10-day-old nestlings. Provisioning rates varied with brood size (P = 0.026) with rates higher for broods of five than broods of three or four. Most prey items delivered to nestlings were grasshoppers (Orthoptera, 68.1%).

Populations of Loggerhead Shrikes (Lanius ludovicianus) across North America have been declining, and factors responsible for this decline remain unclear. Few studies have focused on the availability and use of wintering habitat. Our objectives were to ascertain the size and characteristics of Loggerhead Shrike territories, and examine the hunting behavior of shrikes during the non-breeding season. We observed 1,372 hunting attempts by 19 shrikes; arthropods (65.3%) and other invertebrates (23.3%) were the most common prey. Characteristics of habitat at used and randomly selected, apparently unused isolated and continuous perch sites differed (P = 0.023 and P = 0.021, respectively). Used perches had less grass cover, more bare ground, and denser, shorter vegetation. We found no difference between characteristics of occupied and unoccupied areas (P = 0.34). Non-breeding territories in our study were larger (mean = 85 ha) than those reported for shrikes during the breeding season. The avail...

We studied the effects of breeding stage and behavioral context on the singing behavior of male Indigo Buntings (Passerina cyanea; n = 15) during the 2004 breeding season in Madison County, Kentucky, USA, to better understand how males with a single-song repertoire vary the characteristics of their song to convey different information. Playback experiments were conducted in 2005 in territories of focal males (n = 14) to further examine the possible effect of male-male interactions on singing behavior. We analyzed 10,919 songs of 15 male Indigo Buntings with songs consisting of a series of figures that were usually paired (i.e., phrases). Mean song duration was 2.30 ± 0.13 (SE) sec (range = 1.44–3.40 sec) with males varying song duration by varying the number of figures and phrases in each song. Singing rates varied significantly (P < 0.0001) among breeding stages and were highest prior to pairing, suggesting singing has a role in mate attraction. Singing rates also differed (P = 0.013) du...

Many birds utter alarm calls when they encounter predators, and previous work has revealed that variation in the characteristics of the alarm, or "chick-a-dee," calls of black-capped (Poecile atricapilla) and Carolina (P. carolinensis) chickadees conveys information about predator size and threat. Little is known, however, about possible information conveyed by the similar "chick-a-dee" alarm call of tufted titmice (Baeolophus bicolor). During the winters of 2008 and 2009, free-ranging flocks (N &equals; 8) of tufted titmice were presented with models of several species of raptors that varied in size, and titmice responses were monitored. Smaller, higher threat predators (e.g., eastern screech-owl, Megascops asio) elicited longer mobbing bouts and alarm calls with more notes (D-notes) than larger lower threat predators (e.g., red-tailed hawk, Buteo jamaicensis). During playback experiments, titmice took longer to return to feeding after playbacks of alarm calls given in response to a small owl than to playbacks given in response to a large hawk or a robin (control). Like chickadees, titmice appear to utter alarm calls that convey information about predator size and threat. Titmice, however, appear to cue in on the total number of D-notes given per unit time instead of the number of D-notes per alarm call. The broadband alarm calls of titmice, containing D-notes uttered in an unpredictable manner that may make it difficult for predators to determine the number of titmice calling, may be particularly well suited for deterring predators. Copyright 2010, Oxford University Press.

Individuals of many group-living species of birds respond to potential predators by giving alarm calls, and some species give different, spatially referential alarm calls in response to aerial predators (raptors in flight) and terrestrial predators (including perched raptors). In black-capped chickadees, Poecile atricapillus, characteristics of alarm calls also vary with predator size and level of perceived threat (Templeton et al. 2005, Science, 308, 1934–1937). We examined whether the terrestrial alarm calls of Carolina chickadees, P. carolinensis, show similar variation. In 2007 and 2008, we monitored responses of eight flocks of Carolina chickadees in Madison County, Kentucky, U.S.A. to mounts of different species of raptors that varied in size. Chickadees responded to the raptors by uttering ‘chick-a-dee’ calls with different numbers and types of notes. Larger, lower-threat predators (e.g. red-tailed hawk, Buteo jamaicensis) elicited calls with significantly more introductory ‘chick’ notes and fewer ‘dee’ notes, whereas smaller, higher-threat predators (e.g. eastern screech-owl, Megascops asio) elicited calls with few or no ‘chick’ notes and significantly more ‘dee’ notes. In addition, playback experiments revealed that a greater percentage of Carolina chickadees responded to playback of ‘chick-a-dee’ calls previously given in response to a small predator than during playback of calls given in response to a large predator. These results suggest that the ‘chick-a-dee’ alarm call is a graded signal that informs conspecifics about the presence and behaviour (i.e. perched) of a predator and the degree of threat posed by that predator.

Songs of individual male Blue Grosbeaks (Passerina caerulea) typically begin with the same combination of elements, but the sequence and number of elements in the latter portion of songs vary. We examined the possible functions of within-song variation in Blue Grosbeaks at the Blue Grass Army Depot near Richmond, Kentucky, USA from 15 April to 31 July 2007. We examined singing rates and song characteristics of second-year (SY; n 5 6) and after-second-year (ASY; n 5 14) males, and conducted playback experiments (n 5 15) to identify the possible function of variation in song length. Male Blue Grosbeaks sang at highest rates prior to pairing, maintained relatively high singing rates during the post-pairing/pre-nesting and nest-building/egg-laying stages, and sang at lower rates during the incubation, nestling, and fledgling stages. These results suggest high singing rates are important in attracting mates and establishing territories, and lower singing rates may result from trade-offs associated with parental care. Males used longer songs during aggressive encounters with conspecifics and responded more aggressively to playback of longer songs. This suggests songs containing more elements signal increased aggression. Within-song variation may be an important way to vary song meaning for male Blue Grosbeaks, and perhaps other males in species with a single song type but repertoires of several different song elements. Received 13 February 2009. Accepted 17 June 2009. Singing by male songbirds serves a variety of functions, ranging from establishing territories and attracting mates (Smith 1991) to distracting predators (Ritchison 1991), communicating with young (Beecher 1990), coordinating nest ex- changes with mates (Smith 1988), and informing

The causes of variation in rates of extra-pair paternity among avian populations remain unclear, but could include environmental factors such as breeding density and synchrony. By experimentally manipulating nest site availability, we tested the effects of breeding density on the frequency of extra-pair paternity in eastern bluebirds (Sialia sialis). We also examined the role of breeding synchrony on extra-pair paternity using natural timing of nests. Microsatellite analysis revealed 34 of 305 nestlings (11.2%) were the result of extra-pair fertilizations; and 21 of 79 broods (26.6%) had at least one extra-pair nestling. Several measures of breeding density had independent effects on extra-pair paternity. First, experimental plot type affected extra-pair paternity, with 28 of 34 (82.4%) extra-pair young from nests in high density areas, and only six (17.6%) from nests in low density areas. Independently of plot type, the number of breeding neighbors within a 320-m radius was a significant predictor of the likelihood of extra-pair paternity at the nest. Extra-pair paternity was associated with temporal factors such as absolute timing of breeding and natural levels of local breeding synchrony, but only in bivariate comparisons. We found a positive interaction between density of neighbors within a 320-m radius and local breeding synchrony; this term reduced the main effects of synchrony and number of neighbors, but not experimental treatment. Our results demonstrate the importance of utilizing multiple aspects of proximity in breeding density analyses and testing for interactions between ecological factors that can influence the behavioral events leading to extra-pair fertilizations.

Eastern Phoebes (Sayornis phoebe) persistently pump their tails when perched, and the function of this behavior is unclear. We tested four hypotheses concerning the possible functions of tail pumping, including the (1) balance hypothesis, (2) signal-aggression-to-conspecifics hypothesis, (3) foraging-enhancement hypothesis, and (4) predator-deterrent hypothesis. Eastern Phoebes were monitored from 1 April to 1 August 2006 and 1 June to 1 August 2007 in Madison County, Kentucky. Phoebes were captured in mist nets and marked with unique combinations of colored-leg bands. Each focal phoebe was observed one to two times a week and tail-pumping rates, wind velocity, and perch characteristics were recorded. Our results provided support only for the predator-deterrent hypothesis. Phoebes exhibited a significant increase in tail-pumping rates in the presence of a potential predator (Eastern Screech-Owl, Megascops asio), suggesting that tail pumping, along with increased rates of calling, informs potential predators that a phoebe is aware of their presence and, therefore, more difficult to capture. Phoebes, however, tail pump regardless of whether a predator has been sighted and such movement could make phoebes easier to detect. If so, and if a detected phoebe provides no additional cues (calling) to indicate awareness of a predator, an attack might actually be more likely. However, tail pumping may be beneficial, regardless of whether a predator has been detected, if it serves as a continuous, honest predator-deterrent signal. This would be the case if predators learned to associate tail pumping and phoebes, and also learned that phoebes, with their alert posture, small size, and impressive aerial maneuvering abilities, represent low reward, difficult-to-capture prey. If so, then both phoebes and predators would benefit, with phoebes less likely to be attacked and predators not initiating attacks that would waste time and energy and alert other potential prey to their presence. SINOPSIS Sayornis phoebe mueve su cola persistentemente cuando esta perchado, la funcion de este comportamiento no es clara. Nosotros pusimos a prueba cuatro hipotesis relacionadas con la posible funcion del movimiento de la cola, las cuales fueron (1) hipotesis del balance, (2) hipotesis de senales de agresion en contra de individuos de la misma especie, (3) hipotesis de la intensificacion de busqueda de alimento y (4) la hipotesis para desalentar a los depredadores. S. Phoebe fue monitoreado desde 1 Abril–1 Agosto 2006 y 1 Junio–1 Agosto 2007 en Madison County, Kentucky. S. Phoebe fue capturado con redes de niebla y marcado en sus patas con una combinacion unica de anillos. Cada S. Phoebe focal fue observado 1–2 veces a la semana y las tasas de movimiento de la cola, la velocidad del viento y caracteristicas de las perchas fueron colectadas. Nuestros resultados solo proveyeron soporte para la hipotesis de desalentar a los depredadores. S. Phoebe mostraron un notable incremento en la tasa movimiento de su cola ante la presencia de un depredador potencial (Megascops asio), lo cual sugiere que le movimiento de la cola, adicional al incremento simultaneo de llamados, informan a depredadores potencias que S. Phoebe esta al tanto de su presencia y consecuentemente sera mas dificil de capturar. Debido a que S. Phoebe mueve su cola sin importar la presencia de un depredador, depredadores potenciales que detecten a un S. Phoebe el cual no este proveyendo senales adicionales como llamados o moverse mas cerca, puede ser percibido como una indicacion que no han sido detectados y probablemente incremente la probabilidad de un ataque. Sin embargo, una posible ventaja del movimiento persistente de la cola, incluso cuando un depredador potencial no ha sido detectado, es que sirve como una senal honesta e igualmente persistente para desalentara a los depredadores. Este seria el caso si potenciales, pero no detectados, depredadores perciben el movimiento de la cola como una senal de que S. Phoebe, debido a su postura de alerta, tamano pequeno (< 20 gms), y habilidades de maniobrabilidad bien desarrolladas, como una dificultad para capturar una presa potencial y como resultado el no atacar resultaria mas benefico (en terminos de no perder tiempo y energia) que atacar.

Ascertaining the functions bird song requires information about when and where a song or, for males with multisong repertoires, songs are used. Because the need for and type of communication with mates and conspecifics changes with breeding stage and social context, detailed observations may reveal differential use of song or of different song types. Our objective was to examine the use, and determine the possible functions, of the two song types (primary and sustained) in the repertoire of male grasshopper sparrows (Ammodramus savannarum) by observing males throughout the breeding season and in different behavioral contexts in Madison County, Kentucky. For primary songs, rates varied among breeding stages and were highest before pairing, suggesting that primary song plays a role in mate attraction. However, male Grasshopper Sparrows continued to use primary songs after pairing, and likely functions include territory defense. The use of sustained songs also varied among breeding stages, with none uttered before pairing and rates highest during nest building and incubation. Male grasshopper sparrows also uttered more sustained songs when being observed (with one of us in their territories) then when not (neighboring males). These results suggest that sustained songs may serve to alert females to the presence of potential predators while simultaneously distracting such predators. Songs with such functions appear to be uncommon and have been reported in few other species.

Current procedures for reclaiming surface mines have produced many hectares of open grasslands. Asio flammeus (Short-eared Owl) and Circus cyaneus (Northern Harrier) are regularly found in such grasslands, but little is known about the suitability of these areas as raptor habitat. Our objective was to quantify the hunting behavior of Short-eared Owls and Northern Harriers, and characterize the vegetation in areas used by foraging Short-eared Owls during the non-breeding season on a reclaimed surface mine in Muhlenberg and Ohio counties, KY, from 1 January–1 May 2002. Northern Harriers and Short-eared Owls foraged in flight during our study, with no instances of perch-hunting observed, and initiated attacks primarily in areas dominated by either Lespedeza sp. (sericea) or Festuca sp. (fescue). Attack success rates were 7% and 10.9% for Harriers and Short-eared Owls, respectively, both within the range of success rates previously reported. Analysis revealed that areas used by foraging Short-eared O...

Carotenoid-based coloration of skin and plumage has been found to be correlated with individual quality in many species of birds during the breeding season. However, less is known about the possible role of these signals during the nonbreeding season, particularly among nonpasserines that defend winter territories. American Kestrels (Falco sparverius) are sexually dimorphic raptors that defend winter territories and possess carotenoid-based morphological features known to be correlated with individual quality. Much is known about winter territory use and habitat segregation by male and female kestrels, but possible relationships among morphological features, individual quality, and habitat quality have not been examined. Our objective was to examine possible relationships between morphology, territory quality, and skin color of American Kestrels. Male kestrels had brighter skin than females, and the skin color of male kestrels was positively correlated with size (wing chord and tail length) and territorial quality (hunting territories with less canopy and more grass cover). No such relationships were found for female kestrels. Skin color appears to be an honest indicator of quality for male American Kestrels and may serve both intersexual (territory acquisition) and intersexual (mate choice) functions during the breeding and nonbreeding seasons. SINOPSIS. Posible relaci´

Grasslands are among the most threatened habitats in North America and populations of many grassland birds, including Northern Harriers (Circus cyaneus), are declining. While native grasslands are disappearing, current procedures for reclaiming surface mines have produced large areas of grasslands in the eastern United States. Currently, little is known about the use of such grasslands by raptors. The objective of this study was to examine the nesting behavior of Northern Harriers on a reclaimed surface mine grassland in Kentucky. Over two breeding seasons (April–July 2002–03), 46 harrier nests were located, and young fledged from 10 (21.7%) of these nests. All but one nest were located in dry, upland areas, and the increased vulnerability of nests in such sites to predation may have contributed to this relatively low nesting success. Successful nests were located in denser vegetation than unsuccessful nests, suggesting that greater concealment may reduce predation risk. The percentage of breedin...

Long-term pair bonds and defense of territories year-round are common among tropical passerines. The boundaries of these territories tend to be stable, perhaps reflecting the need to defend an area that, regardless of conditions, provides sufficient food resources. If, however, these stable territories are not, even temporarily, sufficiently large, then intra-pair competition for available food may result, particularly in species with no sexual size dimorphism. With such competition, sex-specific differences in foraging behavior may result. Male and female Dusky Antbirds (Cercomacra tyrannina) are not size dimorphic, and pairs jointly defend territories throughout the year. Our objective was to determine if paired Dusky Antbirds exhibited sex-specific differences in foraging behavior. Foraging antbirds were observed in central Panama from February–July 2002 to determine if pairs partitioned food resources. Males and females exhibited no differences in foraging behavior, with individuals of both sexes foraging at similar heights and using the same foraging maneuvers (glean, probe, and sally) and substrates (leaves, rolled leaves, and woody surfaces). These results suggest that Dusky Antbirds do not partition resources and that territory switching, rather than resource partitioning, may be the means by which they gain access to additional food resources.

Populations of Grasshopper Sparrows (Ammodramus savannarum) have been declining, and ag- ricultural practices, such as grazing by domestic cattle (Bos taurus), are likely contributing factors. Grazing can alter the composition and structure of vegetation and influence prey availability, and such changes can impact the nesting success of grassland birds. Our objective was to examine the nesting success of Grasshopper Sparrows in grazed and ungrazed habitats on the Blue Grass Army Depot in Madison County, Kentucky. Clutch sizes of female Grasshopper Sparrows nesting in grazed and ungrazed areas differed significantly, with mean clutch sizes of 4.48 in ungrazed areas and 3.91 in grazed areas. In addition, nest success was higher in ungrazed areas (70%) than grazed areas (25%). Insect sweeps revealed that invertebrate biomass in ungrazed areas was greater than in grazed areas, and analysis of vegetation indicated that grazed areas had less litter, more shrubs, and shorter, less dense vegetation than ungrazed areas. Most unsuccessful nests were depredated, and the higher predation rates on nests in grazed areas may have been due to differences in vegetation structure. Shorter, less dense vegetation in grazed areas may make it easer for predators to observe adults and locate nests, while taller, denser vegetation in ungrazed areas may provide greater concealment. While the results of previous studies suggest that light to moderate grazing can produce habitat suitable for Grasshopper Sparrows, more intense grazing, as on our study area (one animal unit/ha), creates habitat less suitable for these sparrows.

In birds, males and females may benefit by choosing mates based on morphological characteristics correlated with their ability to provide parental care. Our objective was to examine possible relationships between morphological characteristics and the provisioning behavior of male and female Yellow-breasted Chats (Icteria virens). No differences were found in the provisioning behavior of male and female Yellow-breasted Chats. Adult chats provisioned nestlings at higher rates and delivered more biomass at first nests than during later nesting attempts. This indicates that, later in the breeding season, nestling chats may require less energy, perhaps because warmer temperatures lower thermoregulatory costs. No correlations, either positive or negative, between chat morphological characteristics (mass, eye stripe length, tail length, wing chord, tarsus length, and plumage color) and provisioning behavior were noted. Thus, these results do not provide support for either the honest advertisement hypoth...

Populations of Henslow's Sparrows (Ammodramus henslowii) are declining, and loss of habitat is a likely factor. Coal mine reclamation has created grassland habitat in Kentucky and elsewhere, and information is needed concerning the use of these areas by Henslow's Sparrows. We compared the behavior and ecology of populations on reclaimed sites and non-mined sites in west-central Kentucky during the 2000 and 2001 breeding seasons. Territories were smaller on the reclaimed sites than unmined sites, perhaps due to differences in habitat quality. Insect sweeps revealed more prey biomass on reclaimed sites than unmined sites. Twenty-eight of 48 nests (58%) fledged at least one young, and nesting success was similar on reclaimed and unmined sites. Mean clutch size was 3.75, with no difference between reclaimed and unmined sites. Similarly, the mean number of fledglings per nest was similar on reclaimed and unmined sites. Multivariate analysis revealed differences in the characteristics of vegetation on ...

Extra-pair paternity is widely documented in birds, but the behaviors that lead to extra-pair copulations (EPCs) have been less well studied, particularly in territorial songbirds. We studied the behaviors associated with extra-territorial forays (ETFs) and male mate guarding in a socially monogamous, but genetically promiscuous, neotropical migrant passerine, the yellow-breasted chat (Icteria virens). Focal observations and radiotelemetry revealed that both males and females engaged in ETFs. 65% of the females in our study engaged in at least one foray onto a neighboring territory. 50% of males also were observed engaging in ETFs, but males were much more conspicuous during these intrusions compared to females. Females preferred to remain close to the ground in areas where vegetation was the densest. Female behavior was difficult to observe during ETFs but females sometimes interacted with neighboring extra-pair males. Males attempted to guard their mates by remaining close to them and following them during extra-territorial intrusions. We observed instances in which a male attacked his mate and appeared to herd her back to his territory. However a male's ability to maintain close proximity to his mate was significantly and negatively correlated with vegetation density. Our results suggest that the behaviors which lead to extra-pair encounters are influenced by the behavior of all participants and are modified by the characteristics of the habitat.

Sexual dimorphism or dichromatism has long been considered the result of sexual selection. However, for many organisms the degree to which sexual dichromatism occurs has been determined within the confines of human perception. For birds, objective measures of plumage color have revealed previously unappreciated sexual dichromatism for several species. Here we present an unbiased assessment of plumage dichromatism in the yellow-breasted chat Icteria virens. Chats exhibit yellow to orange throat and breast plumage that to the unaided human observer differs only subtly in color. Spectrophotometric analyses revealed that chat throat and breast feathers exhibited reflective curves with two peaks, one in the ultraviolet and one in the yellow end of the spectrum. We found differences in both the shape and magnitude of reflectance curves between males and females. Moreover, for feathers collected from the lower edge and middle of the breast patch, male plumage reflected more light in the ultraviolet and yellow wavelengths compared to females, whereas male throat feathers appeared brighter than those of females only in the ultraviolet. Biochemical analyses indicated that the plumage pigmentation consisted solely of the carotenoid all-trans lutein and we found that males have higher concentrations of plumage carotenoids than females. Feathers that were naturally unpigmented reflected more UV light than yellow feathers, suggesting a potential role of feather microstructure in UV reflectance.

Previous authors have noted the unique singing behavior and apparently large song repertoires of male Yellow-breasted Chats (Icteria virens). We studied the singing behavior of 10 male chats in central Kentucky in an attempt to determine the size and functions of their song type repertoires and examine possible relationships among singing behavior, morphological characteristics, and reproductive success. During the 1995 breeding season, we recorded and analyzed chat songs and determined the morphological characteristics and reproductive success of focal males. Repertoire sizes varied among male chats, ranging from 46–81 song types. Larger males (as determined by tarsus length) had larger song type repertoires, and males with longer wing chords fledged more young. These relationships suggest a correlation between male quality (as determined by size and reproductive success) and repertoire size. Male chats spent less time singing after pairing, suggesting that singing plays a role in mate attractio...

Five male Eastern Bluebirds (Sialia sialis) were observed and songs recorded over entire breeding seasons in central Kentucky. Songs consisted of an average of 3.02 notes and the mean time between the beginning of successive songs within a bout was 7.26 s. Most songs (63.7%) given by male bluebirds were low volume, while 14.8% were moderate volume, and 21.5% were high volume. Individual male bluebirds possessed large (x = 59.4) repertoires of song types, and few were shared among two or more males. Singing rates varied among breeding stages, with high rates during the pre-pairing period suggesting that song plays a role in mate attraction. However, male bluebirds also sing during interactions with conspecific males, indicating an aggressive or territorial function, to facilitate the transfer of food to incubating or brooding females, nestlings, and fledglings, and to warn mates, nestlings, or fledglings about the presence of a potential predator. Thus, as reported in an increasing number of spec...

We videotaped an Eastern Phoebe (Sayornis phoebe) nest in central Kentucky on 22 June 2008 and documented a case of infanticide. An adult male phoebe, likely the resident male, was captured at the nest site on 21 June 2008. The resident female fed nestlings (3, ∼8 days of age) 69 times during a 4.1-hr taping session (0815–1221 hrs EDT) the next day, but the resident male was not observed at the nest. Beginning at 0923 hrs, an intruding phoebe (likely a male) occasionally visited the nest, sometimes pecking at, but not feeding, the nestlings; this phoebe initiated a vigorous attack at 1151 hrs, pecking and pulling the head of one of the nestlings for 25 min before pulling it out of the nest. The intruding phoebe returned after a short absence, just before the end of the videotape, and began attacking another nestling. The nest was empty when checked the next day. Suitable territories and nest sites may be limiting factors for Eastern Phoebes, and infanticide by non-breeding males may enhance their...

The effects of habitat and vegetation characteristics on the reproductive success of Yellow-breasted Chats (Icteria virens) were examined in central Kentucky. During the 1998 breeding season, 49 nests were located and monitored and the characteristics of nest sites and territories determined. Habitats where nests were located were categorized as old field, linear, or clump, and nests were classified as early or late. Chat nests were located in areas with more foliage and lateral cover than unused sites. However, most nests (55%) were not successful, and variables that differed between nest sites and random locations did not appear to influence nesting success. A diverse and, in an evolutionary sense, novel community of predators may eliminate predictably safe nest sites for chats on our study area. Chats in territories with more foliage cover and less canopy cover were more likely to fledge young. Dense foliage may lower the chances of nest predation by increasing the number of potential nest sites in a territory and may also provide better foraging habitat.

We used genetic analysis to examine the mating strategies of male and female Eastern Screech-Owls (Otus asio) in central Kentucky. DNA fingerprinting revealed no evidence of extra-pair fertilizations in 23 broods (80 nestlings). Such results suggest that pursuit of extra-pair copulations by male and female screech-owls may be costly. One possible cost for females is the risk of losing the nest site. Alternatively, pursuit of extra-pair matings by females might be energetically expensive, thereby conflicting with egg production. Male screech-owls provide food for their mate (and young) during much of the breeding season and such feeding probably affects reproductive success. Males pursuing EPCs might have less time for foraging and, as a result, reduced reproductive success.

The vocal repertoire of male Common Yellowthroats (Geothlypis trichas) includes a single distinctive perch song, a flight song, and several calls, including a chatter call. To ascertain the function of perch songs and chatter calls and to determine if these vocalizations are altered to convey different information, I examined the singing and calling behavior of male yellowthroats throughout the breeding cycle and in different behavioral contexts. The singing behavior of males changed in two ways after pairing: singing rates declined, suggesting that perch songs play a role in mate attraction, and most songs were uttered with reduced volume. These low volume songs appeared to be directed at mates, perhaps serving to stimulate ovulatory cycles, elicit copulation solicitation, or provide information about potential predators. Male yellowthroats uttered regular volume songs at low rates after pairing, suggesting that their function is not limited to mate attraction. Regular volume songs uttered after pairing appeared to be used in both intrasexual and intersexual contexts. The use of chatter calls did not decline until after females began incubating, and most were directed at conspecific males in aggressive (territorial) contexts. Male yellowthroats typically uttered longer perch songs (more phrases per song) during the nest building/egg laying and incubation/nestling periods, however, the possible function of these longer songs is unknown. My results provided no other evidence that male yellowthroats convey motivational information by varying the temporal and frequency characteristics of either perch songs or chatters

We studied patterns of mate guarding and paternity in 21 pairs of Northern Cardinals (Cardinalis cardinalis) nesting in central Kentucky. DNA fingerprinting revealed that five of 37 nestlings (13.5%) resulted from extra-pair fertilizations (EPFs). Of 19 broods sampled, three (16%) had at least one extra-pair young. Although our observations of male cardinals making extra-territorial movements suggest that some males in the population may actively pursue EPFs, the percentage of extra-pair young in our study was lower than reported for many other passerines. Three non-exclusive factors may have contributed to this low percentage. 1. Male cardinals may gain more from parental efforts than from pursuing extra-pair copulations (EPCs). 2. Females in resident species such as Northern Cardinals probably have more opportunities to assess the quality of prospective mates prior to pairing than do females in migratory species and so EPCs may be less likely to be beneficial to females. 3. Most male cardinals exhibited mate guarding behavior. Males maintained contact with fertile mates 72.8% of the time during initial nesting attempts and, in addition, males followed females more often than females followed males in nine of 10 pairs.