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Parental and territory quality are often correlated in territorial birds, and both factors influence the resources allocated to offspring. Surprisingly, the relative contribution of these two components of variation in parental investment remains obscure. We experimentally decoupled the normal covariation between parental quality and territory quality to test the hypothesis that territory quality influences female prenatal and postnatal reproductive allocation. Territories were categorized into low-, intermediate-, and high-quality based on fledging success of nests over the previous 6 years (nesting sites are fixed in space).To decouple covariation between territory quality and individual quality, nestbox entrance size was increased on high-quality territories and left small on poor-quality sites because house wrens (Troglodytes aedon) prefer small over large entrances to their nest sites. We found a significant prenatal effect of territory quality on nestling provisioning: when reared on intermediate-quality territories, nestlings hatching from eggs produced on low-quality territories were provisioned at a higher rate than those hatching from eggs produced on high-quality territories. We propose that the increased provisioning was brought about by increased nestling begging mediated by a maternally derived compound, such as corticosterone, transferred to the eggs of stressed females in poor-quality habitat. [ABSTRACT FROM AUTHOR]

Experiments designed to quantify the effects of increasing numbers of carers on levels of offspring care are rare in cooperative breeding systems, where offspring are reared by individuals additional to the breeding pair. This paucity might stem from disagreement over the most appropriate manipulations necessary to elucidate these effects. Here, we perform both carer removal and brood enhancement experiments to test the effects of numbers of carers and carer:offspring ratios on provisioning rates in the cooperatively breeding chestnut-crowned babbler (Pomatostomus ruficeps). Removing carers caused linear reductions in overall brood provisioning rates. Further analyses failed to provide evidence that this effect was influenced by territory quality or disruption of group dynamics stemming from the removals. Likewise, adding nestlings to broods caused linear increases in brood provisioning rates, suggesting carers are responsive to increasing offspring demand. However, the 2 experiments did not generate quantitatively equivalent results: Each nestling received more food following brood size manipulation than carer removal, despite comparable carer:offspring ratios in each. Following an at-hatching split-design cross-fostering manipulation to break any links between prehatching maternal effects and posthatching begging patterns, we found that begging intensity increased in larger broods after controlling for metrics of hunger. These findings suggest that manipulation of brood size can, in itself, influence nestling provisioning rates when begging intensity is affected by scramble competition. We highlight that carer number and brood size manipulations are complimentary but not equivalent; adopting both can yield greater overall insight into carer effects in cooperative breeding systems. [ABSTRACT FROM AUTHOR]

The costs of reproduction are an important constraint that shapes the evolution of life histories, yet our understanding of the proximate mechanism(s) leading to such life-history trade-offs is not well understood. Oxidative stress is a strong candidate measure thought to mediate the costs of reproduction, yet empirical evidence supporting that increased reproductive investment leads to oxidative stress is equivocal. We investigated whether territory quality and offspring provisioning increase oxidative stress in male snow buntings ( Plectrophenax nivalis) using a repeated sampling design. We show that arrival oxidative stress is not a constraint on territory quality or the number of offspring fledged. Nevertheless, owners of higher-quality territories experienced an oxidative cost, with this cost increasing more rapidly in younger males. Males that provisioned offspring at a high rate also experienced increased oxidative stress. Together, these findings support the potential role of oxidative stress in mediating life-history trade-offs. Future work should consider that reproductive workload is not limited to offspring care, and other activities - including territory defence - may contribute significantly to the costs of reproduction. [ABSTRACT FROM AUTHOR]

The article presents a study to examine the correlation between natal dispersal distances of a population of Swainson's hawk monitored from 1979 to 2010 in northern California. It examines the effects of sex, number of offspring fledged, population density, primary productivity around a nest site and annual trends on dispersal from the natal site to the breeding site. Results show no correlation between natal dispersal distance and lifetime reproductive success of the hawks.

In this paper, we study proximate causes and consequences of breeding dispersal and divorce in a Mediterranean blue tit Cyanistes caeruleus population. We attempt to evaluate the primacy of mate and territory quality in the decision making of birds. In females, the fidelity to their old territories was dependent on how they did in the previous year. We found differences in hatching success and fledging success between females that dispersed and those that did not. In particular, dispersal distance was negatively correlated with hatching success in the preceding breeding season. Dispersed females experienced a gain in terms of hatching success and increased productivity in comparison with those that retained their former mate. Both females and males improved the quality of their breeding site after dispersal. We also found evidence that divorce is adaptive for at least one pair member because adult females (but not juveniles) enhanced their breeding performance after the breakup. Such improvement was also observed when restricting the analyses to only those individuals that did not change territory, suggesting that these benefits not only accrue through the acquisition of better territories but advantages derived from pairing with a higher rank male (mate effects per se) could also be important. Our results suggest that 1) both dispersal and divorce can be regarded as adaptive decisions, 2) females play an active role in pair-bond maintenance, and 3) the intense competition for good nesting sites drives the observed high divorce rate (63%) reinforcing the view that breakups could be a side effect derived from the female’s attempt to improve their breeding place. [ABSTRACT FROM PUBLISHER]

The article presents a study on nest-site selection and quantified nest and survival of Sarus Cranes located in Uttar Pradesh in India. Study shows that cranes preferred wetlands as nesting habitat at the levels of both the landscape as well as individual territory. It is noted that the hatching of broods had a lower probability of survival.

Despite the potential reproductive benefits of extrapair matings, extrapair paternity rates in many avian species often vary greatly among populations. Although ecological factors have been shown to influence intraspecific patterns of extrapair paternity in some species, for cooperatively breeding species living in family groups, social/demographic factors may also play a role. This study examined how ecological factors related to territory quality (vegetation cover, insect abundance) and social/demographic factors (group size, number of breeding pairs, genetic relatedness) influenced intraspecific patterns of extrapair paternity in cooperatively breeding superb starlings, Lamprotornis superbus. Superb starlings inhabit spatiotemporally variable African savannas where high temporal variability drives reproductive decisions (adoption of breeding roles, offspring sex allocation) and where territories suitable for breeding are limited. Although extrapair paternity rates were only 14% of offspring and 25% of nests, they varied greatly among groups, ranging from 4% to 32% of offspring and from 7% to 60% of nests. These among-group differences in extrapair paternity were not related to social/demographic factors but instead to territory quality; extrapair paternity was higher on lower quality territories (lower vegetation cover and grasshopper abundance) than on higher quality territories (higher vegetation cover and grasshopper abundance). These results suggest that even in a heterogeneous landscape where suitable breeding territories are limited, subtle differences in habitat quality can have profound effects on reproductive decisions and patterns of extrapair paternity. Understanding the interaction between spatial (habitat heterogeneity) and temporal (temporal variability) environmental variation will be important for determining how environmental and social factors drive avian reproductive and mating decisions. [ABSTRACT FROM PUBLISHER]

Habitat selection models, such as the ideal free, ideal despotic, site-dependent, and conspecific cuing models, are of great importance to behavioral ecologists given their capability to predict habitat distributions and to link individual behavior to population processes. However, there have been relatively few field tests of their predictions. We tested the 4 models by studying the process of sequential settlement on territory in 2 distant populations of a migratory raptor, the black kite Milvus migrans. Results were mainly consistent with the site-dependent model: on arrival, kites settled on progressively lower quality territories, and earlier arriving individuals were older, larger, and in better body condition than later arriving ones, leading to a state-dependent arrival sequence also predicted by a previous theoretical model of settlement pattern. Occupation of superior territories by superior phenotypes resulted in cascading advantages for earlier arriving individuals in terms of subsequent reproductive performance. At the population level, the populations expanded/retracted from lower quality sites during population increases/declines. The above scenario was consistent across the 2 populations, and a review of the literature uncovered a remarkably consistent picture of state-dependent arrival, progressive monopolization of best quality sites, and cascading effects on subsequent breeding performance. We propose as a general paradigm of sequential settlement the following process: 1) arrival date is a reliable surrogate of phenotype quality, 2) early-arriving individuals have preferential access to the best quality sites and partners, 3) the above conditions cascade into a number of benefits ultimately related to higher fitness for earlier arriving individuals. [ABSTRACT FROM PUBLISHER]

Abundant evidence suggests that females may engage in mate choice to gain nongenetic (material) benefits from high-quality territories; however, the selective consequences that influence those choices are not well understood. We studied the fitness effects of territory quality and incubation temperature on juvenile lizards in nature. We manipulated territory quality by redistributing rocks between pairs of neighboring home ranges. Rock manipulations set up adjacent plots that were either experimentally improved or reduced in quality. We incubated eggs from field-caught gravid females in each of three temperature treatments in the laboratory (low, medium, and high temperature). Progeny were released in either experimentally improved or reduced-quality plots upon hatching, and the following spring we measured survival as a function of egg size and laying date. We conducted concurrent studies of the thermal environment on experimental territories. Improved territories provided significantly more hours for lizards to behaviorally thermoregulate at their preferred body temperature and also provided nest sites with incubation conditions that were closer to optimal compared with reduced-quality plots. Reduced-quality plots were significantly more variable in quality. Finally, we measured significant correlational selection between egg mass and laying date on manipulated plots in two separate years. Results indicate the influence of environmental variation on correlational selection on life-history traits. [ABSTRACT FROM AUTHOR]

It is well understood that females may gain direct benefits from breeding with attractive males. However, the direct fitness effects of mate-choice are rarely considered with respect to mating between different species (hybridization), a field dominated by discussion of indirect costs of producing unfit hybrid offspring. Hybridizing females may also gain by the types of direct benefits that are important for intraspecific mate choice, and in addition may have access to certain benefits that are restricted to mating with males of an ecologically diverged sister-taxon. We investigate possible direct benefits and costs female Ficedula flycatchers gain from breeding with a heterospecific male, and demonstrate that hybridizing female collared flycatchers ( F. albicollis) breed in territories that do not suffer the seasonal decline in habitat quality experienced by females breeding with conspecifics. We exclude the hypotheses that heterospecific males provide alternative food-types or assume a greater amount of the parental workload. In fact, the diets of the two species ( F. albicollis and F. hypoleuca) were highly similar, suggesting possible interspecific competition over food resources in sympatry. We discuss the implications of direct fitness effects of hybridization, and why there has been such a disparity in the attention paid to such benefits and costs with regard to intraspecific and interspecific mate-choice. [ABSTRACT FROM AUTHOR]

Spotted Owls (Strix occidentalis) are territorial, generally nonmigratory, and strongly philopatric. Nevertheless, California Spotted Owls (S. o. occidentalis) exhibited breeding dispersal during 7% of interannual observations of banded individuals (n = 54 of 743 occasions). Based on ecological theory and published literature, we made a priori predictions about the factors associated with the probability of breeding dispersal and breeding dispersal distance, and about the consequences of dispersal. Breeding dispersal probability was higher for younger owls, single owls, paired owls that lost their mates, owls at lower quality sites, and owls that failed to reproduce in the year preceding dispersal. Sex had little effect on the probability of breeding dispersal. Dispersal distance was similar for female and male owls (median = 7 km, range = 1–33 km). We found no strong relationships between dispersal distance and any of the conditions that were associated with the probability of breeding dispersal. Dispersal resulted in improved territory quality in 72% of cases. These results indicate that breeding dispersal was condition-dependent and adaptive. [ABSTRACT FROM AUTHOR]

Loss of cached foods is a constant threat to animals that hoard food, and pilfering plays an important role in the evolution of hoarding strategies. Although pilfering is known to affect the behavior of scatter hoarders, pilfering has been assumed to be less important for larder hoarding animals. In this study, I used a mark-recapture study of cached Norway spruce (Picea abies) cones to quantify pilfering rates in larder-hoarding red squirrels (Tamiasciurus hudsonicus). Red squirrels stole 26% of the cones that they ate and lost 25% of the cones cached in their middens. Most squirrels stole cones (97%) and lost cones to stealing (92%). However, individual squirrels stole 1-100% of the cones that they ate and lost 1-84% of the cones cached in their middens. Numbers of cones gained by and lost to stealing were not related to the age or sex of individual squirrels or the distances between or numbers of cones cached in individual territories. Squirrels with small middens, however, ultimately gained cones, and those with large middens lost cones. Because food is frequently a limiting resource for red squirrels, these changes in food abundance may directly affect the fitness of individual squirrels. Thus, pilfering likely plays an important role in shaping the hoarding and defensive behaviors of larder-hoarding animals. [ABSTRACT FROM AUTHOR]

We used morphological and breeding data from a 2-year field study of red-winged blackbirds (Agelaius phoeniceus) to test the hypothesis that males characterized by low levels of bilateral asymmetry (i.e., high developmental competence) realize a reproductive advantage. Specifically, we evaluated each of several distinct components of male reproductive success relative to asymmetry measures made on five bilaterally paired characters. Results of a male removal experiment generally failed to support the prediction that symmetry would be associated with success in competition for access to breeding territories: established territory owners and nonterritorial replacement males were effectively indistinguishable in this regard. Similarly, there was no indication that symmetrical males were more likely to establish territories in high-quality marsh habitat than in marginal upland field habitat. Finally, monitoring of breeding activity in high-quality habitat revealed that male symmetry was generally unrelated to recruitment of social mates (i.e., harem size), the productivity of those mates (average female reproductive success), withinpair paternity (assessed using DNA-based analysis of parentage), or extrapair mating success. Collectively these results indicate that symmetry is not an important determinant of reproductive success among individual male red-winged blackbirds. This observation, in combination with the results of several other recent investigations, suggests that the fitness consequences of subtle departures from perfect symmetry may be less significant and/or less ubiquitous than initially suggested. [ABSTRACT FROM AUTHOR]