Nest Initiation Date Research Articles

Population ecology of breeding Pacific common eiders on the Yukon‐Kuskokwim Delta, Alaska

Les populations d'Eiders a duvet du Pacifique (Somateria mollissima v-nigrum) ont decline de 50-90% sur le delta du Yukon-Kuskokwim (DYK) dans l'ouest de l'Alaska entre 1975 et 1992 puis se sont stabilisees avec des faibles effectifs depuis le debut des annees 1990 jusqu'a aujourd'hui. Nous avons etudie les processus sous-jacents qui affectent la dynamique de ces populations en recoltant et en analysant les donnees demographiques des Eiders a duvet du Pacifique a 3 sites sur le DYK (1991-2004) pour un total de 29 site-annees. Nous avons examine la variation des parametres de la reproduction, teste des hypotheses concernant l'influence de certains facteurs ecologiques specifiques sur les traits d'histoire de vie et evalue leur contribution relative a la dynamique de la population locale. Le succes reproducteur etait faible et variable, tant pour un meme individu qu'entre les individus alors que la survie apparente des femelles adultes etait elevee et peu variable (0.89 ± 0.005). Tous les parametres reproductifs variaient entre les sites d'etude et les annees. Les dates d'initiation des nids s'etalaient du 4 mai au 28 juin, avec un pic (mode) d'initiation le 26 mai. Les femelles qui nichaient a un site insulaire initiaient toujours leurs nids 3-5 jours plus tot que les femelles nichant a 2 autres sites situes sur la terre ferme. La variance de la date d'initiation des nids pour la population etait negativement liee au pic suggerant une synchronisation accrue durant les annees plus tardives. En moyenne, la taille de ponte totale (pondue) variait entre 4.8 et 6.6 oeufs et declinait avec la date d'initiation du nid. En tenant compte de la predation partielle et des oeufs non-viables, le nombre moyen d'oeufs a l'eclosion variait entre 2.0 et 5.8. Pendant la saison de reproduction, la probabilite de survie journaliere (PSJ) des nids etait plus faible durant la ponte et pour les nids inities tardivement. L'estimation de la survie des nids variait considerablement entre les sites et les annees (moyenne = 0.55, ecart: 0.06-0.92), mais la variance du processus de la survie des nids etait relativement faible (0.02, IC: 0.01-0.05), indiquant que la majorite de la variance etait attribuable a l'erreur d'echantillonnage. Nous avons trouve que l'effet des observateurs pouvait reduire le succes global des nids de 0.0 a 0.36 a travers les site-annees. Les sites d'etude avec de plus faibles nombres d'echantillons et les plus frequemment visites semblaient subir un plus grand effet des observateurs. En general, les Eiders a duvet du Pacifique demontraient une grande variance dans leurs parametres de reproduction. Des tailles de ponte plus elevees et une survie des nids elevee pour les pontes initiees tot suggerent une selection directionnelle pour une nidification hâtive. Cependant, les effets environnementaux stochastiques peuvent masquer la reponse a cette force de selection. Nos resultats demontrent que les femelles qui se reproduisent tot en saison ont la plus grande valeur reproductive car elles pondent plus d'oeufs et ont la plus grande probabilite de les amener a eclosion. Nous avons developpe des modeles matriciels stochastiques structures en classes de stades qui incluent la variance spatio-temporelle observee (processus) et la co-variation des indices demographiques puis avons projete la distribution stable des classes de stades (w) et le taux de croissance de la population (X)

Erratum: Comparative survival and recovery of Ross's and lesser snow geese from Canada's central arctic

Traylor, Joshua J., Ray T. Alisauskas, Stuart M. Slattery, and Kiel L. Drake. 2012. Comparative survival and recovery of Ross's and lesser snow geese from Canada's central arctic. Journal of Wildlife Management 76:1135–1144. In this article, the x axis of Figure 6 was incorrectly labeled. The corrected Figure 6 is shown below. The publisher regrets the error. Figure 6. Relationship between juvenile survival probability for Ross's and snow geese marked north of the Karrak Lake goose colony, Nunavut, Canada, 1991–2008, in relation to mean nest initiation date. Survival estimates are model averages back-transformed from the logit scale.

Potential Factors Affecting Nest Initiation Date, Clutch Size and Nest Success in the Plumage Dimorphic Reddish Egret

Abstract. Plumage dimorphism is common in the family Ardeidae with one morph possessing all-white plumage and the alternate morph being darkly colored. The effects of plumage morph and colony site on nest initiation date, clutch size and total nest success of the plumage dimorphic Reddish Egret in the Laguna Madre region of Texas were examined. Color morph did not significantly affect nest initiation date (Julian date - Dark morph: 109.88 (S.D. 26.56), White morph: 100.82 (25.85), Mixed-morph: 113.29 (27.55); ANOVA: F(2,158)= 0.199, P = 0.820) although nest initiation date was different between nesting colonies (Julian date - Rabbit Island: 125.14 (S.D. 18.05); Zigzag Island: 87.15 (19.07); ANOVA: F(1,158) = 5.732, P = 0.018). Overall mean (±S.E.) clutch size was 3.29 ± 0.05 and differed between colony sites but not between color morphs. Model selection analysis using logistic exposure revealed that neither plumage morph nor colony site had a significant effect on nest success. Mayfield total nest success...

Comparative survival and recovery of Ross's and lesser snow geese from Canada's central arctic

AbstractLarge increases in several populations of North American arctic geese have resulted in ecosystem‐level effects from associated herbivory. Consequently, some breeding populations have shown density dependence in recruitment through declines in food availability. Differences in population trajectories of lesser snow geese (Chen caerulescens caerulescens; hereafter snow geese) and Ross's geese (C. rossii) breeding in mixed‐species colonies south of Queen Maud Gulf (QMG), in Canada's central arctic, suggest that density dependence may be limiting snow goose populations. Specifically, long‐term declines in age ratios (immature:adult) of harvested snow geese may have resulted from declines in juvenile survival. Thus, we focused on juvenile (first‐year) survival of snow and Ross's geese in relation to timing of reproduction (annual mean nest initiation date) and late summer weather. We banded Ross's and snow geese from 1991 to 2008 in the QMG Migratory Bird Sanctuary. We used age‐structured mark‐recapture models to estimate annual survival rates for adults and juveniles from recoveries of dead birds. Consistent with life history differences, juvenile snow geese survived at rates higher than juvenile Ross's geese. Juvenile survival of both species also was lower in late seasons, but was unrelated to arctic weather measured during a 17‐day period after banding. We found no evidence of density dependence (i.e., a decline in juvenile survival over time) in either species. We also found no interspecific differences in age‐specific hunting vulnerability, though juveniles were more vulnerable than adults in both species, as expected. Thus, interspecific differences in survival were unrelated to harvest. Lower survival of juvenile Ross's geese may result from natural migration mortality related to smaller body size (e.g., greater susceptibility to inclement weather or predation) compared to juvenile snow geese. Despite lower first‐year survival, recruitment by Ross's geese may still be greater than that by snow geese because of earlier sexual maturity, greater breeding propensity, and higher nest success by Ross's geese. © 2012 The Wildlife Society.

Mate loss affects survival but not breeding in black brant geese

For birds maintaining long-term monogamous relationships, mate loss might be expected to reduce fitness, either through reduced survival or reduced future reproductive investment. We used harvest of male brant during regular sport hunting seasons as an experimental removal to examine effects of mate loss on fitness of female black brant (Branta bernicla nigricans; hereafter brant). We used the Barker model in program MARK to examine effects of mate loss on annual survival, reporting rate, and permanent emigration. Survival rates decreased from 0.847 6 0.004 for females who did not lose their mates to 0.690 6 0.072 for birds who lost mates. Seber ring reporting rate for females that lost their mates were 2 times higher than those that did not lose mates, 0.12 6 0.086 and 0.06 6 0.006, respectively, indicating that mate loss increased vulnerability to harvest and possibly other forms of predation. We found little support for effects of mate loss on fidelity to breeding site and consequently on breeding. Our results indicate substantial fitness costs to females associated with mate loss, but that females who survived and were able to form new pair bonds may have been higher quality than the average female in the population. Key words: black brant, breeding propensity, clutch size, mate loss, nest initiation date. [Behav Ecol]

Implantation reduces the negative effects of bio-logging devices on birds

Animal-borne logging or telemetry devices are widely used for measurements of physiological and movement data from free-living animals. For such measurements to be relevant, however, it is essential that the devices themselves do not affect the data of interest. A recent meta-analysis reported an overall negative effect of these devices on the birds that bear them, i.e. on nesting productivity, clutch size, nest initiation date, offspring quality, body condition, flying ability, foraging behaviours, energy expenditure and survival rate. Method of attachment (harness, collar, glue, anchor, implant, breast-mounted or tailmount) had no influence on the strength of these effects but anchored and implanted transmitters had the highest reported rates of device-induced mortality. Furthermore, external devices, but not internal devices, caused an increase in 'device-induced behaviour' (comfort behaviours such as preening, fluffing and stretching, and unrest activities including unquantifiable 'active' behaviours). These findings suggest that, with the exception of device-induced behaviour, external attachment is preferable to implantation. In the present study we undertake a meta-analysis of 183 estimates of device impact from 39 studies of 36 species of bird designed to explicitly compare the effects of externally attached and surgically implanted devices on a range of traits, including condition, energy expenditure and reproduction. In contrast to a previous study, we demonstrate that externally attached devices have a consistent detrimental effect (i.e. negative influences on body condition, reproduction, metabolism and survival), whereas implanted devices have no consistent effect. We also show that the magnitude of the negative effect of externally attached devices decreases with time. We therefore conclude that device implantation is preferable to external attachment, providing that the risk of mortality associated with the anaesthesia and surgery required for implantation can be mitigated. We recommend that studies employing external devices use devices that can be borne for long periods, and, wherever possible, deploy devices in advance of the time period of interest.

Clutch Size and Nest Survival of Cackling Geese in a Lesser Snow and Ross's Goose Colony

Clutch size and nest survival of Cackling Geese (Branta hutchinsii hutchinsii) nesting among light geese (Lesser Snow Geese (Chen caerulescens) and Ross's Geese (C. rossii;)) were examined at Karrak Lake, Nunavut, in Canada's central arctic, 1999–2009. Islands of Karrak Lake and adjacent Adventure Lake were selected by Cackling Geese for nesting instead of mainland habitat. Cackling Geese increasingly nested on islands during the study, while light goose nesting declined. Clutch size varied by year (range: 3.4–4.4 eggs), and declined with nest initiation date ( NID = -0.l77 (95% CI:-0.228,–0.126)). Nest survival during incubation varied among years (range: 8.6–88.2%), and was lowest during early and late incubation, although 95% CI of slope estimates with nest age included zero ( Age = 0.156 (95% CI -0.072, 0.383), A2 = -0.006, (95% CI -0.027, 0.014)). Nest survival declined with individual nest initiation date ( NID = -0.431 (95% CI: -0.680, -0.182)). There was little support for nest survival models that included individual covariates of synchrony with light geese or weather during incubation. A posteriori analysis revealed that annual nest survival was greater in warmer years with less wind ( YearWeather = 1.738 (95% CI: 1.272, 2.205)), but spring phenology, intraspecific synchrony, or abundance of Cackling or light geese were not important. Reduced access to island-nesting geese by terrestrial predators, and predator satiation from high densities of nesting light geese on the surrounding mainland may result in islands within light goose colonies that are productive nesting habitats for many avian species, particularly if islands themselves are sparsely inhabited by light geese.

Does spring ice cover influence nest initiation date and clutch size in common eiders?

Understanding how environmental factors affect ecological parameters is important to understanding and predicting impacts of environmental change. Given evidence and anticipated impacts of climate variability, this is especially true with respect to sea ice and its role in animal life history in northern regions. We examined relationships between the extent of consolidated spring ice cover (pack and landfast), nest initiation and clutch size in common eiders (Somateria mollissima) in northern Labrador, a sub-Arctic region on the east coast of Canada. Our initial prediction was that eiders would delay nesting and have smaller clutches in years with more extensive spring ice cover. Between 1998 and 2003, we surveyed coastal islands for breeding eiders and collected information on nest age and clutch size. For those years, we estimated ice cover based on Radarsat-1 images supplied by the Canadian Ice Service during the spring period (approximately June 7–12). We found that spring ice cover was a significant positive predictor of nest initiation date, and the regression equation indicated that if the average extent of ice cover around nesting islands increased by 18 ha, average nesting date was delayed by approximately 1 day. Nest initiation date was a significant negative predictor of clutch size, and the regression equation indicated that a 20 day delay in nesting reduced average clutch size by approximately 1 egg. However, ice cover itself was not a significant predictor of clutch size. Our findings suggest that eiders breed when ice is present, but ice extent may negatively influence aspects of their breeding ecology.

Breeding biology of Sabine’s gull (Xema sabini) in the Canadian high Arctic

The Sabine’s gull (Xema sabini) is a small seabird that breeds in select locations across the circumpolar Arctic, but there have been few studies on its breeding biology, particularly from the high Arctic. We studied nesting phenology, breeding effort, and breeding success of Sabine’s gulls over 5 years at a colony on a small island (Nasaruvaalik) in the Canadian high Arctic. Compared to studies in the low Arctic, nest initiation dates and adult body mass were more consistent across years, and reproductive success was typically higher at Nasaruvaalik Island. These differences may be related to the more predictable food sources available in the nearby polynya upon arrival from migration, as well as the lower predation pressure at our site.

Variations in breeding success and daily nest survival of Whiskered Tern (Chlidonias hybrida) at two Iranian colonies

Variations in breeding success of the Whiskered Terns (Chlidonias hybrida) were studied in two wetlands; Anzali (2005 and 2008) and Zarivar (2007–2008) in north and west Iran. Nesting success was modeled and compared using information-theoretic approach implemented in program Mark in order to assess effects of colony locations, years and nest initiation dates on the probability of daily nest survival. Clutch size did not vary between colonies and years. Breeding success varied between colonies (Zarivar > Anzali), and years only in Anzali (2005 > 2008). Overall daily nest survival was 0.977. (95% LCI 0.973, UCI 0.981), equivalent to a Mayfield nest survival of 0.317. (95% LCI 0.255, UCI 0.387). Egg-laying periods and colony site were important covariates affecting the daily survival rates (Σωi = 0.86 and Σωi = 0.83, respectively), while, the support for the effect of year was less (Σωi = 0.41). We concluded that Lake Zarivar provides a more favorable nesting location for Whiskered Terns probably because of little changes in rainfall and water depth during the breeding seasons which influence breeding performance.

Variation in Breeding of the Shrike-like Tanager in Central Brazil

The Shrike-like Tanager (Neothraupis fasciata) is a Cerrado bird considered as near threatened. Its life history is poorly known, especially its reproduction. We monitored reproduction during four breeding seasons (2003-2006) with 120 nests in a protected area in central Brazil. Nesting began at the end of the dry season and start of the rainy season. The incubation (13.0 days) and nestling (11.7 days) periods were shorter than for most neotropical birds, but similar to some other tanagers. Clutch size (2-3 eggs) was similar to most tropical birds. However, clutch size increased and nest initiation date advanced ,30 days in a year of early precipitation compared to 3 other years with regular or late precipitation. The Shrike-like Tanager had breeding flexibility and ability to adapt to changes in temporal precipitation patterns. Received 23 July 2010. Accepted 21 December 2010. Understanding population dynamics is of fun- damental importance in ecology, evolution, and conservation, especially in regions with habitat loss or other anthropogenic degradation. The Shrike-like Tanager (Neothraupis fasciata), the only species in this genus, occurs in the Cerrado (neotropical savanna) and is classified as near threatened (IUCN 2009). It is a generalist forager (Alves 1991) occurring at altitudes from 500 to 1,100 m (Ridgely and Tudor 1994). It constructs a basket-shaped nest ,1 m above ground (Alves and Cavalcanti 1990) and often is a sentinel in mixed species flocks (Alves 1990, Ragusa-Neto 2000). It is monogamous, forms flocks of up to six individuals and is a cooperative breeder (Alves 1990). Clutch size is usually two or three (Alves and Cavalcanti 1990). It is one of the few of the .800 cerrado birds whose breeding has been studied (Marini 1992; Lopes and Marini 2005a;

Yolk and Feather Carotenoids in Relation to Female Condition and Reproduction in the Yellow-headed Blackbird (Xanthocephalus Xanthocephalus)

ABSTRACT. Carotenoids can be important antioxidants and immunostimulants for developing embryos and adult birds, and they are often incorporated into colorful sexual displays as signals of individual quality. The allocation of carotenoids to egg yolks and feathers can be affected by a female's physical condition, which can in turn affect offspring growth and survival. We examined relationships between yolk and feather concentrations of carotenoids and various indices of female quality (i.e., body condition, heterophil-to-lymphocyte ratio, hematocrit, date of nest initiation, egg mass, reproductive success) in the Yellow-headed Blackbird (Xanthocephalus xanthocephalus), a brightly colored passerine. Measures of physical condition of female Yellow-headed Blackbirds were correlated with the allocation of carotenoids to both eggs and feathers. Specifically, less stressed (i.e., lower heterophil-to-lymphocyte ratio) females had higher concentrations of β-carotene in their eggs than females that were more stres...

Nest Survival and Density of Cackling Geese (Branta Hutchinsii) Inside and Outside a Ross's Goose (Chen Rossii) Colony

ABSTRACT. The influence of heterospecifics on successful avian reproduction remains poorly understood, despite the role that such relationships may play in the evolution of reproductive strategies. We estimated nest survival of Cackling Geese (Branta hutchinsii) near McConnell River, Nunavut, in 2004 and 2005 in relation to (1) nest initiation date; (2) nest age; (3) nesting habitat; (4) presence in or absence from a colony composed mainly of Ross's Geese (Chen rossii); and (5) density of neighboring Lesser Snow Geese (C. caerulescens caerulescens) and Ross's Geese. We also assessed whether there was any consistent pattern in nest densities of Cackling Geese inside and outside the colony, using distance sampling methods that account for imperfect detection. Nest survival declined both with later nesting and with increased densities of surrounding Lesser Snow Geese and Ross's Geese, independently of whether or not Cackling Geese nested in the Ross's Goose colony. However, despite these negative interspecif...

Date of Nest Initiation Mediates Incubation Costs of Wood Ducks (Aix Sponsa)

Incubation has a significant reproductive cost in birds that can limit both current and future reproductive success. We manipulated the incubation period of Wood Ducks (Aix sponsa) to examine how female body mass, incubation behavior, and nest temperature responded to changes in incubation costs. We found no relationships between the length of the incubation period and either the percent loss of body mass or the body mass at the end of incubation. However, females that initiated nests early in the season lost more body mass than females that nested later. The number of daily recesses increased slightly with longer incubation periods, but incubation constancy over the full incubation period and during the last week of incubation was not affected by incubation-period length. Variation in incubation constancy was explained best by nest initiation date. Incubation constancy was greatest for early-nesting females and declined for females that nested later. There also was a weak positive relationship between body mass and incubation constancy. Average nest temperature was not associated with the length of the incubation period but increased with increasing incubation constancy and as the breeding season progressed. Evidence from this study is consistent with the idea that incubation is an important reproductive cost that may constrain the timing of nest initiation in Wood Ducks. Poor-quality females, by delaying nest initiation, experienced reduced incubation costs and were able to maintain nest temperatures at levels similar to those of early-nesting females.

Factors influencing investigator-caused nest abandonment by North American dabbling ducks

We examined factors (species, nest age, nest initiation date, clutch size, predator activity) that may affect the probability of investigator-caused nest abandonment in North American dabbling ducks and made predictions based on parental investment theory. For all nests, the best model contained species, nest stage, nest initiation date, and the interaction of species with nest initiation date. The probability of abandonment by Mallards ( Anas platyrhynchos L., 1758) was consistently higher than that of Blue-winged Teal ( Anas discors L., 1766). In these species, abandonment probability increased with later date, whereas Gadwall ( Anas strepera L., 1758), Northern Pintails ( Anas acuta L., 1758), and Northern Shovelers ( Anas clypeata L., 1758) showed the opposite pattern. Abandonment by all species declined as nest stage increased. Early-laying (≤5 eggs) females were 7 times more likely, and late-laying females were twice as likely, to abandon nests as incubating females. During incubation, abandonment probability was 38% higher during early (≤8 days) incubation than late incubation, and for each additional egg in a completed clutch, it was 19% lower. We propose a novel, two-stage model in which dabbling duck nest abandonment is influenced predominantly by opportunities for future reproduction during laying, and expected benefits from the current reproductive event during incubation.

The Connectivity of Spring Stopover Sites for Geese Heading to Arctic Breeding Grounds

During the spring migration arctic-breeding geese pause in temperate and subarctic staging areas in order to deposit body reserves for breeding. Focusing on a single arctic stopover site in West-Spitsbergen, Svalbard, Norway (Vårsolbukta, 77°45′N, 14°24′E), behavioural strategies of Barnacle Geese Branta leucopsis were investigated and body condition and presence of individually marked birds recorded. Individuals using different staging areas earlier along the migration route (Helgeland and Vesterålen on the Norwegian mainland) and heading to different breeding colonies (the close-by Nordenskiöldkysten, and the distant Kongsfjorden) were compared during springs 2003–05. Birds in Vesterålen left the staging area earlier than those in Helgeland, and arrived earlier in Vårsolbukta as well. In Vårsolbukta, females gained body condition at a similar rate regardless of their colony affiliation, whereas males from Nordenskiöldkysten exhibited a smaller overall increase in condition compared to males from Kongsfjorden. The Kongsfjorden birds stayed for a shorter period (average 2.8 days) than those from Nordenskiöldkysten (average 4.0 days). Nordenskiöldkysten birds frequently left Vårsolbukta for short periods presumably visiting the breeding area in order to optimise nest initiation with respect to prevailing snow conditions. The date of final departure was also correlated with nest initiation date at Nordenskiöldkysten. No such relationship for the Kongsfjorden birds was found. We suggest that the geese adopt a ‘hopping’ strategy, using a network of stopover sites in Svalbard during spring with a last stopover at a buffer area in the proximity to the breeding area. For this vulnerable population it is important to identify the sites forming the links in this chain, and to establish their function and utilisation by geese during the vital prebreeding period.

Bobolink Egg Mass Variability and Nestling Growth Patterns

The Bobolink (Dolichonyx oryzivorus) is an obligate grassland species that is declining throughout its range in North America. There are few data available on Bobolink eggs and nestlings; this information is necessary for conservation planning efforts. Egg mass was recorded for 175 eggs from 37 nests in Québec and eastern Ontario in 2006–2007. Hatching asynchrony was evident with high between-clutch variation in egg mass. Egg mass did not differ with clutch size. Nest initiation date was positively correlated with smallest egg size and negatively correlated with within-clutch egg mass deviation. Nestling wing length, tarsus length, and mass were measured for 166 nestlings ranging from 2 to 10 days of age. Bobolink nestlings fledged below adult size and mass, achieving 87.7 ± 2.3%, 67.6 ± 1.5%, and 55.1 ± 0.4% of breeding adult tarsus length, mass, and wing length (± SE), respectively.

Aspects of Common Eider Nesting Ecology in Labrador

The status, distribution, and nesting ecology of common eiders (Somateria mollissima) breeding in Labrador are not well known. This study is an initial effort to improve understanding of the nesting ecology of eiders on the Labrador coast, a zone of intergradation between the northern (S. m. borealis) and American (S. m. dresseri) subspecies of common eider. During 1998 and 1999, 187 islands were surveyed for nesting eiders at four sites (from north to south: Nain, Hopedale, Makkovik, St. Peter’s Bay) along 750 km of the coast. Nest initiation dates (calculated by candling eggs) ranged over a four- to five-week period and were positively associated with latitude: the earliest mean initiation date (5 June) was in St. Peter’s Bay in the south and the latest (27 June) at Nain in the north. Mean clutch size ranged from 3.5 to 4.2 and varied by area and year; eiders nesting in Nain had the smallest clutches. In 1999, the highest nest density (49.8 nests/ha) was observed in Nain and the lowest (3.9 nests/ha) in Makkovik. In some cases, we used boat surveys to assess eider presence and absence and found it to be a reliable method; this search technique could be beneficial to researchers working in remote locations where operational costs are high.

Factors That Affect Renesting in Mallards (Anas platyrhynchos)

ABSTRACT. Renesting is an important strategy for coping with nest loss in many species of birds. We investigated renesting behavior of radiomarked Mallards (Anas platyrhynchos) breeding in the Canadian Prairie Parklands and found that females were persistent renesters, replacing >57% of 4,112 destroyed nests. Renesting propensity was most affected by nest initiation date, with ∼90% of unsuccessful females renesting if destroyed clutches had been initiated in April but <10% renesting for clutches initiated after 20 June. Probability of renesting declined with successive number of nesting attempts, but this was primarily an effect of initiation date. Renesting propensity increased with female age and body condition and declined for birds that had invested more time tending their previous clutch, but the latter effect was pronounced only among late-nesting females. The amount of time required to produce a replacement clutch was primarily a function of whether females were engaged in rapid follicle growth whe...

Nest site competition between cavity nesting passerines and golden paper wasps Polistes fuscatus

Nest boxes provide sheltered nesting sites for both passerines and paper wasps. Although neither wasps nor birds appear to evict the other once one is fully established, it is unclear which is the dominant competitor at the onset of the breeding season. Using wire mesh, we excluded birds but not golden paper wasps Polistesfuscatus from alternating boxes along a transect through edge habitat in North Carolina from 2006 – 2008. If wasps dominate Carolina chickadees Poecile carolinensis and eastern bluebirds Sialia sialis during the early spring (all have similar nest initiation dates), we would expect wasps to settle in both box types at equal frequencies. However, if birds dominate wasps, we would expect wasp nests to be concentrated in “bird‐proof” boxes. We found wasps in bird‐proof boxes significantly more often than in bird‐accessible boxes, indicating that secondary‐cavity nesting birds are able to exclude wasps from available nest sites. Additionally, we found that during the period of nest initiation, birds usurp wasps more often than vice versa.