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Animals often live within close proximity of multiple conspecific individuals, allowing them to eavesdrop on other animals' signalling interactions to guide their own social behaviours. For a young animal that is learning to vocalize, eavesdropping on vocal interactions between adults may provide a rich source of information: young animals might preferentially learn vocalizations that are commonly heard in interactions between adults or that are heard to be effective for attracting mates or defending resources. We used a multispeaker playback experiment with wild Savannah sparrows, Passerculus sandwichensis, to test the hypothesis that vocal learning is guided by eavesdropping. Over a 6-year period, we tutored young Savannah sparrows with experimental tutor songs; half of the tutor songs were broadcast in simulated vocal interactions between two tutors, and the other half were broadcast as noninteractive, stand-alone solo performances. If eavesdropping plays an important role in guiding vocal learning, we predicted that young birds would preferentially learn the vocalizations heard during interactions between tutors. In contrast to our prediction, young Savannah sparrows did not preferentially learn interactive tutor songs; birds were similarly likely to learn songs heard in an interactive context (N = 13) and in a noninteractive context (N = 17). Analysis of live adult tutors' reactions to the loudspeakers showed that they responded with similar vocal behaviour during interactive and noninteractive treatments, and therefore their vocal behaviour did not compromise the playback simulation. We conclude that eavesdropping on vocal interactions between tutors does not appear to be essential for vocal learning of wild Savannah sparrows.

Many birds rely on alarm calls during nest defence to communicate about risk, but anthropogenic disturbance, including noisy industrial infrastructure, has the potential to disrupt alarm communicat...

Different components of learned birdsongs change at different rates across generations, and the rate of change may correspond to the information carried by each component. To characterize the role of the buzz segment of Savannah sparrow songs, we examined recordings from southeastern Canada and the northeastern US and fully characterized buzz segments in songs recorded from two populations: one on Kent Island, NB, Canada and another in Williamstown, MA, USA. Buzzes varied geographically: Kent Island buzzes had higher mean frequencies and shorter pulse periods than Williamstown buzzes and the differences between the two populations persisted over time. Population-specific buzz characteristics also appeared to be resistant to change. Variants appeared on Kent Island in the late 1980s and were learned by some younger birds; however, these buzz variants disappeared by 2011. We conducted a playback experiment and found that males from both populations had longer responses to local buzzes. Therefore, buzz structure varies geographically; population characteristics of the buzz persist through time despite the introduction of variant forms; and territorial males discriminate between buzzes from different populations. The learned buzz segment of the song may thus serve as a population marker for Savannah sparrows.

Human activities change the acoustic environment in many settings around the world. These changes are complex, as different anthropogenic sound sources create different acoustic profiles; therefore, some sound sources may have greater impacts on wildlife than others. Animals may adapt to these altered acoustic environments by adjusting their vocalizations. In the case of bird song, this may be achieved by adjusting the whole song, which may preserve the spectral and temporal relationships between successive syllables, or by adjusting components (syllables) within the song. Determining which syllables are adjusted may help to elucidate the mechanisms, benefits, and limitations of song plasticity. We examined the effects of conventional industrial infrastructure used to extract shallow natural gas and petroleum (natural gas compressor stations, generator-powered oil well pumpjacks, power grid–powered oil well screw pumps, and generator-powered oil well screw pumps), compared with quiet control site...

Organisms encounter noise naturally in the environment. However, increasing prevalence of human-caused noise seems to be resulting in behavioural changes in many animals that can affect survival and reproduction. Not all species react the same way to noise; some adjust their vocal signals while others do not. We hypothesized that species with more variability in their vocal signals would be better able to adjust their signals to be audible over anthropogenic noise. We tested this within a large-scale manipulative experiment by recording songs of two grassland songbirds, Baird’s sparrow (Ammodramus bairdii) and Savannah sparrow (Passerculus sandwichensis), both of which are found in areas increasingly affected by energy extraction noise. We compared these species because Savannah sparrows have more variability in their songs geographically and temporally compared to Baird’s sparrows. We recorded both species’ songs before, during and after high-fidelity playbacks of oil well drilling noise. Surpris...

Knowledge of which cues attract birds back to natal areas is important for conservation because the cues could be manipulated to attract breeders to source habitat or discourage breeders from settling in sink habitat. We examined the influence of intrinsic and extrinsic variables on natal philopatry using two metrics, short-distance natal dispersal and the probability of philopatry to the natal field, in two obligate-grassland bird species breeding in an agricultural landscape: the bobolink, Dolichonyx oryzivorus, and the Savannah sparrow, Passerculus sandwichensis. During 2002–2014, we detected 90 locally hatched Savannah sparrows and 129 locally hatched bobolinks breeding as adults near their places of origin (mean ± SD dispersal distances: Savannah sparrows: 917 ± 851 m; bobolinks: 1251 ± 839 m). For both species, the location of the field on which they bred relative to fields where annual productivity was greater than replacement best explained variation in natal dispersal distance. The probability a Savannah sparrow was philopatric to its natal field increased if it fledged later in the season, while this probability decreased if there was an opposite-sex parent or sibling present on the natal field, or the field was under a late-hay management scheme. None of the variables considered explained variation in bobolink natal philopatry. Natal philopatry and short-distance natal dispersal in these species appear to be influenced by factors that are difficult to manage; however, land managers should attempt to keep management consistent across time to reduce misinformation in dispersal cues.

Many birds rely on anti-predator communication to protect their nests; however, anthropogenic noise from industrial activities such as oil and gas development may disrupt acoustic communication. Here, we conducted acoustic playback experiments to determine whether Savannah sparrows ( Passerculus sandwichensis ) responded to conspecific alarm calls by delaying feeding visits, and whether this response was impaired by noise-producing natural gas compressor stations, generator- or grid-powered screw pump oil wells, and noise amplitude. We played alarm calls, and, as a control, western meadowlark songs, to Savannah sparrows as they approached their nests to feed their nestlings, and measured feeding latency. The greatest impacts on behaviour were detected at the noisiest treatment, compressor stations; feeding latency was shortened here compared with control sites, which may expose nests to greater predation risk. As noise amplitudes increased, Savannah sparrows took longer to feed following meadowlark playbacks, perhaps because noise interfered with interpretation of acoustic cues. The effects of compressor stations on anti-predator behaviour may be best explained by the distracting effects of anthropogenic noise, while increases in feeding latency following meadowlark playbacks may be explained by a heightened response threshold caused by acoustic masking. Industrial infrastructure can influence the reproductive success of wildlife through its impact on perception and interpretation of conspecific signals, but these effects are complex.

In eight groups of animals, including humans and songbirds, juveniles are understood to learn vocalizations by listening to adults [1-4]. Experimental studies of laboratory-reared animals support this hypothesis for vocal learning [5-7], yet we lack experimental evidence of vocal learning in wild animals. We developed an innovative playback technology involving automated loudspeakers that broadcast songs with distinctive acoustic signatures. We used this technology to simulate vocal tutors in the wild and conducted year-long tutoring sessions to five cohorts of free-living migratory Savannah Sparrows in eastern Canada. We confirm that wild birds learn songs by listening to adult conspecific animals, and we show that they pass these songs on to subsequent generations. Further, we provide the first experimental evidence in the wild that the timing of exposure to tutor song influences vocal learning: wild Savannah Sparrows preferentially learn songs heard during both their natal summer and at the outset of their first breeding season. This research provides direct experimental evidence of song learning by wild animals and shows that wild birds learn songs during two critical stages of development early in life. VIDEO ABSTRACT.

Anthropogenic noise is a pervasive pollutant altering behaviour of wildlife that communicates acoustically. Some species adjust vocalisations to compensate for noise. However, we know little about whether signal adjustments improve communication in noise, the extent to which effectiveness of adjustments varies with noise source, or how individual variation in physiology varies with response capacity. We played noise-adjusted and unadjusted songs to wild Passerculus sandwichensis (Savannah Sparrows) after measurements of adrenocortical responsiveness of individuals. Playbacks using songs adjusted to noisy environments were effective in restoring appropriate conspecific territorial aggression behaviours in some altered acoustic environments. Surprisingly, however, levels of adrenocortical responsiveness that reduced communication errors at some types of infrastructure were correlated with increased errors at others. Song adjustments that were effective in communicating for individuals with lower adrenocortical responsiveness at pumpjacks were not effective at screwpumps and vice versa. Our results demonstrate that vocal adjustments can sometimes allow birds to compensate for disruptions in communication caused by anthropogenic noise, but that physiological variation among receivers may alter effectiveness of these adjustments. Thus mitigation strategies to minimize anthropogenic noise must account for both acoustic and physiological impacts of infrastructure.

Few studies have evaluated techniques for estimating detectability of prairie songbirds. We conducted dependent double-observer point counts at 52 plots in prairie pastures in southern Alberta, Canada, in 2012, to test for species-specific, group-specific, and observer-specific differences in perceptibility. Although we did not find strong species or observer effects on perceptibility of most species in the study, we found evidence of differences in perceptibility when we pooled prairie songbirds into groups according to singing behaviors. Observers typically perceived only 40% of quiet songbirds singing from the ground (e.g., grasshopper sparrows and horned larks) but observed 89% of louder species singing from perch sites (e.g., Savannah sparrows) or in flight (e.g., Sprague’s pipits). Dependent double-observer methods would result in little increase in accuracy of abundance estimates for most species, but could be useful in studies where quiet species are more abundant or are targets for conservation management.

The hypothalamic-pituitary-adrenal (HPA) axis has been studied extensively in adults, but the HPA axis in early life is not well characterized, and there is an immense amount of unexplained variation in glucocorticoid levels during early life, especially in wild animals. To characterize population-wide natural variation in early-life HPA axis function, we compared plasma corticosterone levels (at baseline and after 30 min acute restraint-stress) from seven-day-old nestlings (n = 123) from a free-living, marked population of Savannah sparrows (Passerculus sandwichensis). We found a surprising sensitivity of the HPA axis to timing of sample collection across time scales. Even within the accepted 3-min framework to collect baseline samples, time to collect blood had a significant effect on baseline corticosterone concentrations. Daily rhythms also influenced baseline levels, which increased significantly during the relatively short window of sample collection (1100 and 1600). On a broader timeframe, there was a strong effect of hatch date (over a 2 month period) on HPA axis responsiveness, where nestlings hatched later in the breeding season had lower stress-induced corticosterone levels than those hatched earlier. The ecophysiological mechanisms and implications of these patterns warrant future investigation; meanwhile this study highlights the critical need to consider, and potentially restrict, time across scales when collecting blood samples from wild birds to assess stress physiology. (C) 2017 Elsevier Inc. All rights reserved.

Summary 1. Determining how events interact across stages of the annual cycle is critical for understanding the factors that affect individual fitness. However, there is currently little information detailing how breeding events influence migratory behaviour. 2. Using an automated digital telemetry array and an isolated island-breeding population of Savannah sparrows Passerculus sandwichensis, we provide the first direct evidence that the timing of breeding events carries over to influence the timing of migration in a songbird and assess for the first time how weather conditions on the breeding grounds also affect departure dates. 3. Date of migratory departure between September and October was strongly influenced by date of breeding completion in adults and fledging date in juveniles from June to July. 4. With respect to weather, adults departed during the first half of high-pressure systems, while juveniles departed throughout the entirety of high-pressure systems (including rainy evenings on the western edge of systems). 5. By combining both ecological and weather data, we could explain almost all variation in departure date for adults (95%), but weather conditions were not a good predictor of departure date for juveniles. 6. Our results provide strong evidence that the timing of breeding events is an important driver of migration timing and that exact departure dates are fine-tuned according to local weather conditions in adults, but not in juveniles.

Although magnetic compass orientation has been reported in a number of invertebrate and vertebrate taxa, including about a dozen migratory bird species, magnetic orientation capabilities in animals remain somewhat controversial. We have hand-raised a large number of Savannah sparrows (Passerculus sandwichensis) to study the ontogeny of orientation behavior. Young birds with a variety of early experience with visual and magnetic orientation cues have been tested for magnetic orientation during their first autumn migration. Here we present data from 80 hand-raised sparrows, each tested several times in both normal and shifted magnetic fields. Birds reared indoors with no experience with visual orientation cues showed axial north-south orientation that shifted by almost exactly the magnitude of 90° clockwise and counterclockwise shifts in the direction of magnetic north. Other groups of birds with varying early experience with visual orientation cues showed different preferred orientation directions, but all groups shifted orientation direction in response to shifts in the magnetic field. The data thus demonstrate a robust magnetic orientation ability in this species.

Migratory birds might respond to moonlight in at least four ways: (1) a geographical reference for selecting a compass direction, (2) a celestial ‘landmark’ to facilitate maintenance of a preferred heading, (3) a stimulus that distracts migrants and introduces error in compass orientation, or (4) a source of illumination that facilitates nocturnal flight. This study examines the response of migratory savannah sparrows (Passerculus sandwichensis) to moonlight during controlled tests in orientation cages. I found no evidence that savannah sparrows use a lunar compass to select a direction. If savannah sparrows do use the moon as a ‘landmark’ to maintain a direction selected with reference to a different cue, I expected birds to be better oriented on overcast nights when the moon is present than they are when the moon is absent. The results suggest otherwise. Usually, savannah sparrows respond phototactically to the moon by directing their cage activity toward or at a constant angle with respect to the moon's azimuth. Interestingly, the migrant's response to moonlight depended on whether the bird viewed the setting sun earlier that evening.

We monitored return rates of 324 color-banded Ammodramus savannarum (Grasshopper Sparrow), 138 Passerculus sandwichensis (Savannah Sparrow), and 49 Dolichonyx oryzivorus (Bobolink) on mowed and unmowed areas on a reclaimed surface mine during seven breeding seasons. We observed 61 returns among Grasshopper Sparrows, 40 returns among Savannah Sparrows, and 11 returns among Bobolinks. Grasshopper Sparrows and Savannah Sparrows returned to mowed and unmowed areas at about equal rates (21 vs. 18% and 26 vs. 31%, respectively), while Bobolinks returned to unmowed areas at a higher rate than mowed areas (28% vs. 17% respectively). When hatching-year birds were excluded, overall return rates increased slightly for Grasshopper Sparrows and Bobolinks (19 to 20% and 22 to 23%, respectively), but more substantially for Savannah Sparrows (from 29 to 36%). Sixteen of 51 returning Grasshopper Sparrows (31%), 12 of 27 Savannah Sparrows (44%), and 2 of 10 Bobolinks (20%) were observed during multiple years. Thes...

Radio telemetry can be a valuable tool for studying the behavior, physiology, and demography of birds. We tested the assumption that radio transmitters have no adverse effects on body condition in an island population of Savannah Sparrows {Passerculus sandwichensis) . To assess possible changes in condition, 20 radiotagged and 25 nontagged Savannah Sparrows were captured and recaptured throughout the postfledging period. We used four measures of condition: mass, an index of fat free dry mass (measured via heavy water dilution), pectoral muscle depth (measured via ultrasound imaging), and an index of fat mass (measured via heavy water dilution). Using both a generalized linear modeling framework and paired design, we found no significant differences in the body condition of radiotagged and nontagged adults and juveniles. Thus, our results provide evidence that radiotransmitters have no effect on the condition of Savannah Sparrows during the premigratory period. RESUMEN. Efectos de radiotransmisores en la condicion corporal de individuos de Passer- culus sandwichensis durante el periodo pre-migratorio otonal La radiotelemetria puede ser una herramienta valiosa para estudiar la conducta, fisiologia y demografia de aves. Utilizando una poblacion de gorriones (Passerculus sandiwichensis) , pusimos a prueba el postulado de que los radiotransmisores no tienen efecto adverso sobre la condicion corporal de las aves. Para determinar el posible efecto en la condicion de los pajaros, capturamos y recapturamos 20 individuos con radiotransmisores y 25 individuos sin estos, durante el periodo de post-volantones. En el trabajo utilizamos cuatro medidas de condicion: masa, un indice de masa-seca sin grasa (medida a traves de una dilucion de agua pesada), profundidad de los musculos pectorales (determinado con una maquina de ultrasonido) y un indice de masa de lipidos (medida via una dilucion de agua pesada). Utilizando tanto un andamiaje con modelo linear generalizado y un diseno pareado, no encontramos diferencias significativas en la condicion corporal entre los adultos y juveniles con o sin transmisores. Nuestros resultados proveen evidencia de que los radiotransmisores no tienen efecto adverso en la condicion de los gorriones estudiados durante el periodo migratorio.

Females may engage in extrapair copulations to receive indirect benefits in the form of more immunocompetent young. Nestling quality is often assessed by examining immune function using the phytohemagglutinin (PHA) skin test, which can be a predictor of nestling recruitment. However, the PHA test can also be influenced by factors such as nest temperature. We tested the prediction that extrapair young mount greater immune responses to a PHA challenge and recruit at a greater rate than within-pair young in a wild population of Savannah Sparrows (Passerculus sandwichensis). We also investigated ambient temperature and its relationship with immune response. Extra-and within-pair young did not significantly differ with respect to PHA-induced immune response or with respect to recruitment. In contrast to other studies, we found that PHA-induced immune response was not associated with nestling recruitment rates. However, it was positively correlated with minimum ambient temperature for males hatched in...

We used principal coordinates analysis to analyze variation in 11 plumage characteristics of 1,722 Savannah Sparrows (Passerculus sandwichensis) breeding at 55 different sites from throughout the species' range in Canada, Mexico, and the United States. There is clinal interpopulational variation in size with considerable overlap among localities. Savannah Sparrows resident along the Pacific coast of southern California and Baja California, and those from along the coast of Sinaloa and Sonora (i.e., saltmarsh Savannah Sparrows) differ from those throughout the rest of their range (i.e., non-saltmarsh). Variation among populations of non-saltmarsh Savannah Sparrows was clinal with the exception of those from Sable Island, Nova Scotia, which are consistently more pallid than birds from the adjacent mainland. Western Savannah Sparrows are more pallid than those in the east. The median crown stripe of eastern Savannah Sparrows is distinct, whereas the median crown stripe of western Savannah Sparrows g...

Dispersal is a key process in the metapopulation dynamics and genetic structure of spatially segregated populations. However, our knowledge of avian dispersal, particularly in migratory passerines, remains limited. We studied dispersal of Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis) to determine whether agricultural management practices affected dispersal patterns and habitat selection. From 2002 to 2006, we banded adults and nestlings on six focal hay fields and two pastures in the Champlain Valley of Vermont and New York and searched for banded birds within 1.5 km of Vermont field sites during two years. Natal dispersal distances were greater than breeding dispersal in both species, and breeding dispersal distances of Bobolinks were greater than those of Savannah Sparrows. Site fidelity was high in both species, with >80% of detected adults and ∼30% of detected natal dispersers returning to the same field in subsequent years. During natal dispersal, movem...

We used reobservation of color-banded birds to index annual breeding site fidelity of four species of songbirds that nest in the northern mixed-grass prairie of northcentral Montana (1996–2005). Territorial males of Sprague's Pipits (Anthus spragueii), and Savannah (Passerculus sandwichensis), Grasshopper (Ammodramus savannarum), and Baird's (A. bairdii) sparrows were located on five permanent study sites (1998– 2004) and lured into mist-nets using tape broadcasts of conspecific songs and calls. The proportion reobserved was 5.3% (n = 247) across all banded adult males. Grasshopper Sparrows had the highest proportion of returns (8.9%), followed by Savannah Sparrows (5.4%), Baird's Sparrows (5.1%), and Sprague's Pipits (2.1%). Three nestling Savannah Sparrows were reobserved in subsequent years (n = 193), while no nestlings of the other species were reobserved (n = 401). Our return rates were low for all adults in comparison with typical reports of return rates for songbird species of woodland and...

We compared the incubation behaviour of 1-year-old female Savannah Sparrows Passerculus sandwichensis nesting for the first time with that of older females that had nested in previous years on Kent Island, New Brunswick, Canada. Using temperature probes inserted into 32 nests, we determined the length and variability of incubation shifts and recesses over 99 nestdays. At 14 of the nests, known-age females were matched, each pair consisting of an inexperienced yearling and an experienced older female, and nest temperatures were measured simultaneously. In addition, we quantified the duration of night-time incubation and the mean length and variation of more than 1350 incubation shifts and recesses as a function of female age, weather, time of day and date. In all respects, yearling and older females had equivalent incubation behaviour. The similarity between yearlings and older females suggests that fundamental aspects of incubation behaviour may be largely innate and unaffected by prior reproductive experience or other age-related variables.

1. Patterns of resource allocation in different times of the year can provide insights into the effects of simultaneous environmental constraints on reproduction and survival of desert birds. Field metabolic rate (FMR), water influx rate (WIR) and patterns of time allocation of Hoopoe Larks (Alaemon alaudipes Desfontaines) were investigated during spring, when larks were rearing offspring, and during summer, presumably the harshest time for desert birds, in the Arabian Desert.2. FMR was 45% below allometric predictions in spring (1.83 times basal metabolic rate, BMR) and 58% below predictions in summer (1.37 times BMR). WIR was 37% lower than predicted during the nestling period and 55% lower than predicted during summer.3. Activity patterns during spring and summer were bimodal, with birds foraging in the early morning and late afternoon and resting in the shade or attending the nest during midday. Foraging time was similar in spring (32.0% of total daytime) and summer (33.6% of total daytime), despite higher energy and water intakes for parents and offspring in spring, suggesting that food availability was higher in spring. The non-foraging time was entirely spent resting in summer, while in spring half of this time was allocated to caring for offspring and the other half to resting in the shade. Hoopoe Larks fed their offspring 55 times per day and shaded their chicks about 5 h per day to protect them from solar radiation.4. High T(a)s combined with low and unpredictable food availability in deserts may constrain reproduction by limiting the amount of time, water and energy that parents can devote to rearing offspring.

We observed a male sparrow in May 1999 in Stow, Massachusetts, that showed hybrid characteristics resembling both Grasshopper Sparrow (Ammodramus savannarum) and Savannah Sparrow (Passerculus sandwichensis). During 1999 and 2000, this male sang a simplified Song Sparrow (Melospiza melodia) song. However, in 2001 it also sang a typical Savannah Sparrow song and frequently alternated between these two songs. We recorded songs and captured this individual in an area with numerous Song Sparrows and about three pairs of Savannah Sparrows. We compared mitochondrial DNA, morphological measurements, behavior, and audio spectrograms of this hybrid with similar data from Grasshopper, Savannah, and Song sparrows. Genetic analysis indicated that the hybrid's mother was almost certainly a Grasshopper Sparrow. The hybrid showed morphological traits that were within the range of both Savannah Sparrow and Song Sparrow, but generally were more consistent for Savannah Sparrow. We observed this individual frequentl...

The adaptive significance of mechanisms of energy and water conservation among species of desert rodents, which avoid temperature extremes by remaining within a burrow during the day, is well established. Conventional wisdom holds that arid-zone birds, diurnal organisms that endure the brunt of their environment, occupy these desert climates because of the possession of physiological design features common to all within the class Aves. We review studies that show that desert birds may have evolved specific features to deal with hot desert conditions including: a reduced basal metabolic rate (BMR) and field metabolic rate (FMR), and lower total evaporative water loss (TEWL) and water turnover (WTO).Previous work on the comparative physiology of desert birds relied primarily on information gathered on species from the deserts of the southwestern U.S., which are semi-arid habitats of recent geologic origin. We include data on species from Old World deserts, which are geologically older than those in the New World, and place physiological responses along an aridity axis that includes mesic, semi-arid, arid, and hyperarid environments.The physiological differences between desert and mesic birds that we have identified using the comparative method could arise as a result of acclimation to different environments, of genetic change mediated by selection, or both. We present data on the flexibility of BMR and TEWL in Hoopoe Larks that suggest that phenotypic adjustments in these variables can be substantial. Finally, we suggest that linkages between the physiology of individual organism and its life-history are fundamental to the understanding of life-history evolution.

Scattered populations of Rüppell's foxes (Vulpes rueppelli) occur across the deserts of northern Africa and Arabia. Little is known about the biology of these canids, especially the physiological mechanisms that contribute to their ability to live in such harsh environments. For individuals from Saudi Arabia, we tested the hypotheses that Rüppell's foxes have a reduced basal metabolic rate and total evaporative water loss (TEWL), parameters measured in the laboratory, and a reduced field metabolic rate (FMR) and water flux when free-living. Under basal conditions in the laboratory, males, which averaged 1,858 g in body mass, had an oxygen consumption of 914.9 mL O(2)/h, whereas females, which weighed on average 1,233 g, consumed 682.9 mL O(2)/h; rates of oxygen consumption translated to 441.4 kJ/d and 329.4 kJ/d, respectively. TEWL averaged 52.6 g H(2)O/d for males and 47.5 g H(2)O/d for females. We found no evidence that basal metabolism is reduced in Rüppell's foxes, but their TEWL was remarkably low: 50.9% of allometric prediction for males and 64.5% for females. In the wild during winter, males expended energy at a rate of 1,306.5 kJ/d, whereas females had an expenditure of 722.8 kJ/d. Analysis of covariance with FMR as the dependent variable, sex as a fixed factor, and body mass as a covariate showed no statistical difference in FMR between sexes. Water flux did not differ significantly between sexes and averaged 123 mL H(2)O/d, a value 30% lower than the kit fox from the deserts of southwestern North America. FMR was positively related to nocturnal activity levels as FMR (kJ/d) = -2,900.1+55.5 (% of time moving). The water content of prey items varied between 1.9 and 4.1 g H(2)O/g dry matter consumed. Based on these values and knowledge of their diet, we calculated that foxes captured about one rodent and a variety of anthropods per night of foraging.

We tested the hypothesis that birds in arid environments, where primary productivity is low and surface water is scarce, have reduced energy expenditure and water loss compared with their mesic counterparts. Using both conventional least squares regression and regression based on phylogenetically independent contrasts, we showed that birds from desert habitats have reduced basal and field metabolic rates compared with species from mesic areas. Previous work showed that desert birds have reduced rates of total evaporative water loss when exposed to moderate environmental temperatures in the laboratory. We tested whether reduced rates of total evaporative water loss translate into low field water fluxes. Conventional ANCOVA indicated that desert birds have reduced water fluxes, but an analysis based on phylogenetically independent contrasts did not support this finding, despite the wide array of taxonomic affiliations of species in the data set. We conclude that the high ambient temperatures, the low primary productivity, and the water scarcity in desert environments have selected for or resulted in reduced rates of energy expenditure and evaporative water loss in birds that live in these dimes.

We present the first observations of misdirected parental care by Savannah Sparrows (Passerculus sandwichensis) including a rare occurrence of simultaneous incubation. Two females simultaneously incubated eggs, brooded, and fed nestlings, and two males fed nestlings in one nest. These behaviors may have been prompted by strong parental instincts in combination with a stressful breeding environment mediated by hayfield management, as any genetic benefits were unlikely.

The fitness consequences of male parental care are central to life-history models of reproductive effort and the evolution of social and genetic mating systems. However, in a 4-year study (1992-1995) of Savannah sparrows (Passrrculus sandwichmsis) nesting on Kent Island, New Brunswick, Canada, male parental care during the nestling stage was only weakly related to offspring quality and survivorship. Females compensated for poor paternal performance by elevating their feeding rates, and they thus ameliorated selection on male parental care. The likelihood and size of subsequent broods, was also unrelated to male feeding effort, suggesting the absence of some indirect (or "female-mediated") benefits. These results were confirmed by an experiment in which male removal resulted in increased female feeding rates but had little effect on the number or quality of young. In contrast, previous research with multilocus DNA fingerprinting revealed a strong, positive relationship between a male's parental effort and his subsequent fertilization success. Together, this research suggests that the proximate and ultimate targets of male feeding effort can be distinct; traditional assumptions regarding the function of male parental care in birds may therefore be incomplete.

We investigated the effect of blow fly larvae (Protocalliphora spatulata) on nestling savannah sparrows (Passerculus sandwichensis) in Alaska subject to biennially fluctuating prey abundance. Grasshopper populations in some regions of interior Alaska can show a strong biennial periodicity. Growth of nestling savannah sparrows, numbers of blow fly larvae in nests and on nestlings, and grasshopper populations were monitored during four breeding seasons (1990–1993) on the Delta Agriculture Project site near Delta Junction, Alaska. Growth parameters for parasitized and nonparasitized nestlings were compared within and between years. There were no significant differences in growth parameters between parasitized and nonparasitized nestlings between any years. There were also no differences in growth parameters within years, except for tarsus length in 1991 and nestling mass in 1993 (low grasshopper years); in 1993, parasitized nestlings were heavier and the sample size was small. Additionally, there were no differences in fledging success within years. Although parasitism combined with other factors (e.g., food limitation) may have an impact on avian reproduction, our data do not support this.

We experimentally reduced clutch size of Great Tits Parus major to investigate the effects on parental care (including Daily Energy Expenditure, DEE, measured with doubly labelled water), and the relationship between DEE and the residual reproductive Value. The length of a working day was not affected, but the nestling phase was 0.7 days (4%) shorter in experimental clutches. Males fed reduced broods at a lower rate, but DEE and mass (loss) were not significantly affected by the experiment. However, male DEE was positively correlated with feeding frequency, and this relationship did not differ between control and experimental males. This suggests that the experiment resulted in a slight reduction in male DEE, and lack of statistical significance can be attributed to the power of the test applied. Females fed reduced broods at a lower rate, but female DEE and mass (loss) were not affected by the clutch size manipulation. Female DEE was not correlated with feeding frequency, the original number of eggs in the nest or the actual number of young. The division of labour (feeding rate, DEE) was not affected by the clutch size manipulation. Female DEE was significantly higher than male DEE, and this could be caused by the fact that only the female roosts with the young. There was no consistent relationship between DEE and parental survival or future reproductive success. Since the experimental reduction in clutch size led to an increase in residual reproductive Value (more second clutches), but not to a decrease in DEE, this costs of reproduction is apparently not contingent on increased rate of energy turnover. It is suggested that birds with equal DEE may differ in their residual reproductive value as a consequence of variation in energy allocation between reproductive effort and e.g. aspects of physiological maintenance and repair.

Numerous studies have examined sexual size dimorphism in birds and speculated upon the reasons for its existence. Whilst most studies have focused on individual species or groups of related species, a few have attempted to disentangle the various hypotheses that have been put forward to explain its occurrence. Typical of the latter studies is that by Jehl and Murray (1986), in which they argued that sexual size dimorphism was primarily the result of sexual selection (see also Bennett & Owens 2002). Although some studies have looked at patterns in sexual size dimorphism without calculating a figure to represent the difference (e.g. Amadon 1959), most have examined measurements of birds and used these to calculate such a figure. Traditionally in such studies, measurements used have included wing-length, culmen-length, tarsus-length and mass, although McGillivray (1989) took the sum of 18 skeletal measurements and used their male and female means to determine sexual size dimorphism. Wing-length has commonly been used to determine sexual size dimorphism, although lack of repeatability of measurements may render it less useful than skeletal measurements like tarsus-length as in studies of Dunlin Calidris alpina (Blomqvist et al. 1997) and Savannah Sparrows Passerculus sandwichensis (Rising & Somers 1989); however, Gosler et al. (1998) found wing-length measurements to be more repeatable than other metrics in a group of 27 passerines.

We used multiple and logistic regression analysis to study the breeding-area requirements of 10 species of grassland and early-successional birds at 90 grassland-barren sites in Maine. The incidence of six of the species was clearly sensitive to the area of grassland. Upland Sandpipers, the species with the largest area requirements, were infrequent at sites of less than 50 ha and reached 50% incidence at those of about 200 ha. Grasshopper Sparrows reached 50% incidence at about 100 ha, Vesper Sparrows at about 20 ha, and Savannah Sparrows at about 10 ha. Incidence for three edge species, Brown Thrasher, Common Yellowthroat, and Song Sparrow, was negatively correlated with open area, and incidence for Field Sparrows was not strongly influenced by grassland size. These results indicate that grasslands need to be approximately 200 ha in area if they are to be likely to support a diverse grass land bird fauna. However, large grasslands or grassland-barrens are rare; random samples indicated that in Maine only 1% of hayfields and only 8% of grassland-barrens were more than 64 ha in area. Conservation efforts seeking to protect habitat for rare grassland birds need to consider sites of at least 100 ha—and preferably 200 ha—in size, and these are notably rare in Maine and probably throughout New England and eastern North America. Airports provide some of the last extensive patches of grassland habitat in the northeast. To maintain viable populations of area-sensitive grassland birds, management of these sites for nesting birds will become increasingly important. En el presente estudio utilizamos analisis de regresion multiple y logistica para estudiar los requerimientos de las areas de cria de 10 especies de aves de pastizales y aves comunes durante los estadios sucecionales tempranos en 90 sitios de pastizales-aridos en Maine, EUA. La tasa de ocurrencia de 6 especies fue claramente sensitiva al area del pastizal. Los sandpipers de tierras altas, la especie con los requertmientos de area mas grandes, fue poco frecuente en sitios de menos de 50 ha y llego al 50% de incidencia en sitios con unas 200 ha. Los Grasshopper sparrows alcanzaron una tasa de ocurrencia del 50% en sitios con 100 ha, los Vesper Sparrows lo hicieron en sitios con 20 ha y los Savannah Sparrows en sitios con 10 ha. La tasa de ocurrencia para tres especies de los bordes, Brown Thrasher, Common Yellowthroat y Song Sparrow, estuvo negativamente correlacionada con el area abierta y la tasa de ocurrencia, para los Field Sparrows, no estuvo fuertemente influenciada por el tamano del pastizal. Estos resultados indican que los pastizales necesitan cubrir mas de 200 ha para poder mantener una fauna de pajaros diversa. Sin embargo, las grandes extenciones de pastizales o pastizales-aridos son raras; muestras al azar indican que en Maine solo un 1% de los campos de heno y un 8% de los pastizales-aridos ocuparon mas de 64 ha. Los esfuerzos de conservacion que busquen proteger el habitat de pajaros raros de los pastizales, necesitan considerar sitios de por lo menos 100 ha, preferentemente 200 ha, y estos son notablemente raros en Maine y probablemente a lo largo de Nueva Inglaterra y el este de Norte America. Los aeropuertos proveen algunos de los ultimos extensos parches del habitat de pastos en el nordeste. El manejo de estos sitios se hara crecientemente importante para mantener poblaciones viables de pajaros, sensibles al area de los pastizales.

In the northeastern United States, grassland birds regularly use agricultural fields as nesting habitat. However, birds that nest in these fields regularly experience nest failure as a result of agricultural practices, such as mowing and grazing. Therefore, information on both spatial and temporal patterns of habitat use is needed to effectively manage these species. We addressed these complex habitat use patterns by conducting point counts during three time intervals between May 21, 2002 and July 2, 2002 in agricultural fields across the Champlain Valley in Vermont and New York. Early in the breeding season, Bobolinks (Dolichonyx oryzivorus) used fields in which the landscape within 2500 m was dominated by open habitats. As mowing began, suitable habitat within 500 m became more important. Savannah Sparrows (Passerculus sandwichensis) initially used fields that contained a high proportion of suitable habitat within 500 m. After mowing, features of the field (i.e., size and amount of woody edge) became more important. Each species responded differently to mowing: Savannah Sparrows were equally abundant in mowed and uncut fields, whereas Bobolinks were more abundant in uncut fields. In agricultural areas in the Northeast, large areas (2000 ha) that are mostly nonforested and undeveloped should be targeted for conservation. Within large open areas, smaller patches (80 ha) should be maintained as high-quality, late-cut grassland habitat.

SUMMARYThe interaction and hierarchy of celestial and magnetic compass cues used by migratory songbirds for orientation has long been the topic of an intense debate. We have previously shown that migratory Savannah sparrows, Passerculus sandwichensis, use polarized light cues near the horizon at sunrise and sunset to recalibrate their magnetic compass. Birds exposed to a ±90 deg. shifted artificial polarization pattern at sunrise or sunset recalibrated their magnetic compass, but only when given full access to celestial cues, including polarized light cues near the horizon. In the current study, we carried out cue conflict experiments with white-throated sparrows, Zonotrichia albicollis, during both spring and autumn migration in a transition zone between the species' breeding and wintering areas on the south shore of Lake Ontario. We show that white-throated sparrows also recalibrate their magnetic compass by polarized light cues at sunrise and sunset. Sunrise exposure to an artificial polarization pattern shifted relative to the natural magnetic field or exposure to a shift of the magnetic field relative to the natural sky both led to recalibration of the magnetic compass, demonstrating that artificial polarizing filters do not create an anomalous, unnatural orientation response. Our results further indicate that there is no evidence for a difference in compass hierarchy between different phases of migration, confirming previous work showing that polarized light cues near the horizon at sunrise and sunset provide the primary calibration reference both in the beginning and at the end of migration.

Life-history theory assumes that organisms trade-off current against future reproduction to maximize fitness. Experimental explorations of the costs of reproduction have not yielded a clear understanding of the nature of these costs but rather point to a complex set of allocation possibilities among several physiological functions and behaviors. We investigated how experimentally increased flight costs affected the trade-off between parental investment and self-maintenance in tropical house wrens, which have relatively high annual survival and multiple breeding opportunities per year. We predicted that handicapped wrens would not increase their energy expenditure but instead decrease their effort to rear young in order to maintain their own body condition. Our results largely supported these predictions: handicapped parents decreased their nestling feeding frequency but did neither alter their field metabolic rate (FMR) nor compromise their body condition as measured by basal metabolic rate (BMR) and several measures of innate immune function. Reduced feeding rates did not affect nestling body mass growth but resulted in decreased structural growth (length of tarsus). The latter result can be explained if parents shifted the type of prey brought to offspring or altered the amount of food brought per trip. The experiment-wide positive correlations among FMR, BMR, and feeding frequency are in agreement with the hypothesis that hard work requires elevated levels of BMR. These correlations, in combination with the absence of a handicap treatment effect on FMR or BMR, do not lend support for predictions from studies in the laboratory that birds compensate hard work during the day by lowering their BMR at night. Considering a complex set of allocation possibilities among several physiological functions and behaviors, we conclude that tropical wrens take out the costs of a handicap largely on their offspring quality not on self-maintenance processes. Copyright 2008, Oxford University Press.

The predicted relationship between mortality risk and sparrow community structure is simple. It is as- sumed that the risk of predation is nonrandom across a given landscape because of the patchiness of veg- etation used as cover, and that prey species segregate spatially according to their specific abilities to utilize areas of varying risk. Unfortunately, unlike seed use and availability, predation risk is very difficult to quantify. This is so because observations of predatory

A probabilistic model was validated for estimating avian mortality associated with the application of the avicide CPTH (3-chloro-4-methylaniline hydrochloride) to minimize sprouting rice damage in the southern United States. CPTH exposures for individual birds were predicted by random sampling from species-specific non-parametric distributions of bait seed consumption and CPTH residues detected on individual bait seeds. Mortality was predicted from the species-specific exposure versus mortality relationship. Individual variations in this response were captured in the model by Monte Carlo sampling from species-specific distributions of slopes and median toxicity values (LD50) for each bird. The model was used to evaluate the effects of formulation, bait preparation and application procedures on target and non-target mortalities. The results of these analyses indicate that: 1) decreasing the concentration of CPTH on the treated bait seeds from 400 to 300 μg CPTH/seed will improve bait performance by decreasing non-target mortalities, 2) the current dilution ratio of 1 treated seed to 25 diluent seeds is optimal and 3) preparing a bait seed product in which CPTH is homogeneously distributed throughout the bait seed mixture will significantly increase bait performance by increasing red-winged blackbird (target) mortality and decreasing mortality for savannah sparrows and meadowlarks (non-targets).

1. Patterns of resource allocation in different times of the year can provide insights into the effects of simultaneous environmental constraints on reproduction and survival of desert birds. Field metabolic rate (FMR), water influx rate (WIR) and patterns of time allocation of Hoopoe Larks (Alaemon alaudipes Desfontaines) were investigated during spring, when larks were rearing offspring, and during summer, presumably the harshest time for desert birds, in the Arabian Desert. 2. FMR was 45% below allometric predictions in spring (1.83 times basal metabolic rate, BMR) and 58% below predictions in summer (1.37 times BMR). WIR was 37% lower than predicted during the nestling period and 55% lower than predicted during summer. 3. Activity patterns during spring and summer were bimodal, with birds foraging in the early morning and late afternoon and resting in the shade or attending the nest during midday. Foraging time was similar in spring (32.0% of total daytime) and summer (33.6% of total daytime), despite higher energy and water intakes for parents and offspring in spring, suggesting that food availability was higher in spring. The non-foraging time was entirely spent resting in summer, while in spring half of this time was allocated to caring for offspring and the other half to resting in the shade. Hoopoe Larks fed their offspring 55 times per day and shaded their chicks about 5 h per day to protect them from solar radiation. 4. High T(a)s combined with low and unpredictable food availability in deserts may constrain reproduction by limiting the amount of time, water and energy that parents can devote to rearing offspring.

1. Patterns of resource allocation in different times of the year can provide insights into the effects of simultaneous environmental constraints on reproduction and survival of desert birds. Field metabolic rate (FMR), water influx rate (WIR) and patterns of time allocation of Hoopoe Larks (Alaemon alaudipes Desfontaines) were investigated during spring, when larks were rearing offspring, and during summer, presumably the harshest time for desert birds, in the Arabian Desert. 2. FMR was 45% below allometric predictions in spring (1.83 times basal metabolic rate, BMR) and 58% below predictions in summer (1.37 times BMR). WIR was 37% lower than predicted during the nestling period and 55% lower than predicted during summer. 3. Activity patterns during spring and summer were bimodal, with birds foraging in the early morning and late afternoon and resting in the shade or attending the nest during midday. Foraging time was similar in spring (32.0% of total daytime) and summer (33.6% of total daytime), despite higher energy and water intakes for parents and offspring in spring, suggesting that food availability was higher in spring. The non-foraging time was entirely spent resting in summer, while in spring half of this time was allocated to caring for offspring and the other half to resting in the shade. Hoopoe Larks fed their offspring 55 times per day and shaded their chicks about 5 h per day to protect them from solar radiation. 4. High T(a)s combined with low and unpredictable food availability in deserts may constrain reproduction by limiting the amount of time, water and energy that parents can devote to rearing offspring.

Patterns of time allocation to different activities can help reveal how natural selection has solved optimality problems that involve simultaneous environmental constraints. To investigate how time budgets of desert birds are affected by ambient temperature, lack of drinking water and low food availability, we provided food and water to hoopoe-larks, Alaemon alaudipes, in the Arabian Desert during years in which no larks reared young. We followed birds continuously from sunrise to sunset on unsupplemented and supplemented days, and recorded their behaviour every 15 s. Taking into account the variation in temperature between days, hoopoe-larks decreased foraging time by 13-29% of total daytime, and increased resting and preening time by 7-16 and 8%, respectively, when they had access to supplemental food. When birds had access to extra food, they began and ended their midday resting period when shade temperature was on average 2.2degreesC lower, and operative temperature was on average 3.1degreesC lower, than on unsupplemented days, a significant effect of food supplementation. We concluded that birds optimized time spent on foraging and thermoregulating based on a combination of physiological state variables, including body temperature, hydration state and level of energy reserves. Our results do not support a previous hypothesis that activity budgets of desert birds are dictated by thermal constraints alone. 2002 The Association for the Study of Animal Behaviour.

The avian hippocampal formation is known to participate in naturally occurring spatial behavior such as homing in pigeons and cache recovery in food storing passerines, but its participation in the often spectacular migrations of birds remains uncertain. As a first investigation into the possible role of hippocampal formation in migration, the effect of hippocampal formation lesions on the geomagnetic migratory orientation of Savannah sparrows was examined. When tested indoors, hippocampal formation-lesioned sparrows were able to orient in an appropriate migratory direction indicating no necessary role for hippocampal formation in geomagnetic migratory orientation. However, hippocampal formation-lesioned birds displayed significantly less migratory (nocturnal) activity, a result that inspires further study.

I used the meme concept to investigate patterns of cultural variation among the songs of eight, geographically distinct populations of savannah sparrows. Memes composed of only one syllable were geographically widespread and randomly distributed among populations, but memes of two-, three- and four-syllables became progressively more restricted in their geographical distribution. Thus, the populations were memetically more similar with respect to one-syllable memes and more divergent with respect to larger memes. These results suggest that differences in memetic mutation rates and susceptibility to loss by memetic drift could be sufficient to create the observed pattern of greater divergence among populations for large memes. Copyright 1998 The Association for the Study of Animal Behaviour.

On 17 occasions in Chula Vista, California, at least one Belding's Savannah Sparrow (Passerculus sandwichensis beldingi) was observed chasing egg-carrying female fiddler crabs (Uca crenulata) and pecking eggs from ones it caught. Sparrows did not eat any part of the adult crab while eating the eggs. A fledgling learned this novel hunting technique after accompanying its parent for a month.