Differences In Nesting Success Research Articles

Effects of early‐successional shrubland management on breeding wood thrush populations

ABSTRACTIn forested landscapes, creation of habitat for early‐successional shrubland birds is controversial because of perceived conflicts with the conservation of mature‐forest birds. Nonetheless, many mature‐forest birds, especially fledglings, readily use early‐successional stands during the post‐breeding period. This suggests that for mature‐forest birds, creating habitat for early‐successional birds could involve a tradeoff: reduced abundance and nest survival due to the loss of nesting habitat versus enhanced fledgling survival in early‐successional stands. Our research addressed the effects of the creation of early‐successional habitat for shrubland birds on wood thrushes (Hylocichla mustelina) in western Massachusetts, USA. We compared wood thrush abundance, nest success, fecundity, and post‐fledging survival in landscapes with high (∼20%) or low (∼1%) cover of early‐successional stands suitable for shrubland birds. We found no differences in nest success, fecundity, and post‐fledging survival between the 2 types of landscapes. Abundance of breeders, however, was significantly greater on the sites with high cover of early‐successional habitat. We conclude that in forested landscapes, creation of early‐successional habitat at levels recommended for the conservation of shrubland birds is compatible with viable wood thrush populations. © 2018 The Wildlife Society.

Does best‐practice crow Corvus corone and magpie Pica pica control on UK farmland improve nest success in hedgerow‐nesting songbirds? A field experiment

The role of predation by corvids on the breeding output of songbirds is unclear. Using a randomised‐pair design, we measured how nest success of hedgerow‐nesting passerines responded to the experimental removal of carrion crows and magpies. We worked in southern England at 32 paired sites around 4 km2 each, one with and one without best‐practice corvid control, studying four different pairs per year for four years 2011–2014. We counted corvids, and using songbird territory mapping and fledged brood counts without finding nests along transects, we estimated nest success as a brood/ territory ratio for the community of songbirds in 4 km of hedgerow at each site. Crows and magpies were still present at most removal sites but numbers were half as high as at paired non‐removal sites. Eighteen songbird species were frequently encountered at most sites with on average (±1 SD) 102 ± 30 territories per site. Using a generalised linear mixed model analysis the songbird community as a whole bred less well in treatment sites without corvid removal and in years with more rainfall. Nest success was down by 10% in non‐removal sites on average relative to removal sites over the four years. Excluding 2012 data because of exceptionally high spring rainfall that year, nest success was down 16% in the non‐removal sites on average in the other three years. For open‐cup nesting species as a group there was no difference in nest success between site types. Our data on hole nesters suggest that they were affected by treatment and contributed to our overall result. For species whose numbers are regulated through territoriality, nest‐site or habitat availability, spring abundance is unlikely to be affected by a 15% increase in breeding output. For species limited by nest success, it may be more important.

The effect of incubation temperatures on nest success of flatback sea turtles (Natator depressus)

Oviparous species are threatened in a warming world if their nesting distribution does not change or if they cannot adapt to changing environmental conditions. Consequently, documenting the thermal characteristics of nests and nesting habitats is an important area of research for threatened species, as is the identification of temperatures that embryos are unable to tolerate. Here we used generalised additive mixed models to examine the relationship between nest success (hatching success, emergence success and late-stage mortality) and nest temperature, nest depth and clutch size of flatback sea turtles (Natator depressus) collected over three breeding seasons (2012/2013–2014/2015) at an island rookery (Delambre Island, 20°26′56.38′′S, 117°4′42.29′′E) and on a nearby mainland rookery (Bells Beach, 20°36′51.77′′S, 117° 9′7.55′′E) in north-western Australia. We also examined seasonal and rookery differences in nest success with data collected over six breeding seasons (2009/2010–2014/2015). Mean nest temperature over the entire incubation period was the best predictor of hatching success and emergence success (explaining 37.15 and 39.15 % deviance in results, respectively), with both variables declining beyond about 32.5 °C. Mean temperature in the final third of incubation was the best predictor of late-stage mortality, explaining 73.91 % deviance with mortality increasing when nest temperatures exceeded 34 °C. Our results provide important data for identifying the optimum conditions for embryonic survival in this species, thereby aiding the assessment of the vulnerability of this Data Deficient species to global warming.

A Meta‐Analysis of the Effects of Common Management Actions on the Nest Success of North American Birds

Management strategies for the recovery of declining bird populations often must be made without sufficient data to predict the outcome of proposed actions or sufficient time and resources necessary to collect these data. We quantitatively reviewed studies of bird management in Canada and the United States to evaluate the relative efficacy of 4 common management interventions and to determine variables associated with their success. We compared how livestock exclusion, prescribed burning, removal of predators, and removal of cowbirds (Molothrus ater) affect bird nest success and used meta-regression to evaluate the influence of species and study-specific covariates on management outcomes. On average, all 4 management interventions increased nest success. When common species and threatened, endangered, or declining species (as defined by long-term trend data from the North American Breeding Bird Survey) were analyzed together, predator removal was the most effective management option. The difference in mean nest success between treatment and control plots in predator-removal experiments was more than twice that of either livestock exclusion or prescribed burning. However, when we considered management outcomes from only threatened, endangered, or declining species, livestock exclusions resulted in the greatest mean increase in nest success, more than twice that of the 3 other treatments. Our meta-regression results indicated that between-species variation accounted for approximately 86%, 40%, 35%, and 7% of the overall variation in the results of livestock-exclusion, prescribed-burn, predator-removal, and cowbird-removal studies, respectively. However, the covariates we tested explained significant variation only in outcomes among prescribed-burn studies. The difference in nest success between burned and unburned plots displayed a significant, positive trend in association with time since fire and was significantly larger in grasslands than in woodlands. Our results highlight the importance of comparative studies on management effects in developing efficient and effective conservation strategies.

Density-dependent nest predation in waterfowl: the relative importance of nest density versus nest dispersion

When nest predation levels are very high or very low, the absolute range of observable nest success is constrained (a floor/ceiling effect), and it may be more difficult to detect density-dependent nest predation. Density-dependent nest predation may be more detectable in years with moderate predation rates, simply because there can be a greater absolute difference in nest success between sites. To test this, we replicated a predation experiment 10 years after the original study, using both natural and artificial nests, comparing a year when overall rates of nest predation were high (2000) to a year with moderate nest predation (2010). We found no evidence for density-dependent predation on artificial nests in either year, indicating that nest predation is not density-dependent at the spatial scale of our experimental replicates (1-ha patches). Using nearest-neighbor distances as a measure of nest dispersion, we also found little evidence for "dispersion-dependent" predation on artificial nests. However, when we tested for dispersion-dependent predation using natural nests, we found that nest survival increased with shorter nearest-neighbor distances, and that neighboring nests were more likely to share the same nest fate than non-adjacent nests. Thus, at small spatial scales, density-dependence appears to operate in the opposite direction as predicted: closer nearest neighbors are more likely to be successful. We suggest that local nest dispersion, rather than larger-scale measures of nest density per se, may play a more important role in density-dependent nest predation.

Effects of invasive woody plants on avian nest site selection and nesting success in shrublands

AbstractExotic, invasive plants are a growing conservation problem. Birds frequently use invasive plants as nest substrates, but effects of invasives on avian nesting success have been equivocal in past studies. In 2004 and 2005, we assessed effects of invasive woody plants on avian nest‐site selection and nesting success in western Massachusetts shrublands. At the nest scale, we tested the effects of invasive versus native substrates on nesting success as well as differences among individual invasive species. At the patch scale, we tested effects of invasive prevalence on nesting success in natives and invasives. We found that, as a whole, shrubland birds preferred invasive substrates. Of two species sufficiently abundant for individual analysis, gray catbirds Dumetella carolinensis preferred invasive substrates, but chestnut‐sided warblers Dendroica pensylvanica showed no preference for natives or invasives. At the nest scale, nests of gray catbirds placed in invasive substrates were more successful than those in natives. Chestnut‐sided warblers and all species combined, however, had equal nest success in invasives and natives. We found no differences in nest success for nests in different species of invasive substrates or in invasive substrates with and without thorns. At the scale of the patch, nest success in invasive substrates increased with the prevalence of invasives on a site. Nest success in native plants did not change with invasive prevalence. We attribute this finding to the tendency for thickets of invasive plants to be larger on sites with more invasive cover. These findings illustrate the complex interaction of different factors that can determine how invasive plants affect avian nesting success. We conclude that control of invasive woody plants should be neutral for most shrubland birds.

Influence of food and nest predation on the life histories of two large honeyeaters

Nests of Red Wattlebirds (Anthochaera carunculata) and Noisy Friarbirds (Philemon corniculatus) were watched during four breeding seasons near Armidale, New South Wales (NSW). Friarbirds have larger clutches than Wattlebirds (mode of three v. two) and a shorter breeding season. Two hypotheses (food and nest predation) could explain these differences in life history between the species. We predict that if the food hypothesis is correct Friarbirds would experience a greater seasonal range in food abundance, and hence more abundant food during the breeding season. We also predict that Friarbirds should spend longer incubating, brooding and guarding chicks, because they need to spend less time feeding. If the nest predation hypothesis is correct, Wattlebirds would suffer higher nest predation, and so should spend more time incubating, brooding and guarding their nests, and should visit the nest more synchronously and attack more nest predators. Synchronous visits to the nest reduce the likelihood that predators will be attracted to the nest. We found that Friarbirds spent a greater percentage of time incubating and brooding in the first week after nestlings hatched, and had longer incubation and brooding bouts than Wattlebirds. Wattlebirds left their nests unattended for a greater percentage of the time during incubation, but there was no difference during the nestling stage. There were no differences in the number of incubation bouts per hour, nor in the number of brooding bouts per hour between species. Friarbirds more often visited the nest synchronously during the nestling stage. There was no difference in nest success between the species, with most failures resulting from predation. These results support more of the predictions of the food hypothesis than the nest predation hypothesis. Friarbirds feed themselves and their young on large insects, such as cicadas and scarab beetles, which are abundant for only a short period in the study area, when Friarbird young are dependent. Wattlebirds feed their young on a wide range of insects, including many small ones, which are available over a longer period. The range of clutch-sizes and breeding seasons shown by honeyeaters generally, and friarbirds specifically, provide the opportunity for further testing of these and other hypotheses.

The role of intense nest predation in the decline of Scarlet Robins and Eastern Yellow Robins in remnant woodland near Armidale, New South Wales

A study of open-nesting Eastern Yellow Robins Eopsaltria australis and Scarlet Robins Petroica multicolor, on the New England Tablelands of New South Wales in 2000?02, found low breeding success typical of eucalypt woodland birds. The role of intense nest predation in the loss of birds from woodland fragments was investigated by means of predator-exclusion cages at robin nests, culling of Pied Currawongs Strepera graculina, and monitoring of fledging and recruitment in the robins. Nest-cages significantly improved nest success (86% vs 20%) and fledging rate (1.6 vs 0.3 fledglings per attempt) for both robin species combined (n = 7 caged, 20 uncaged). For both robin species combined, culling of currawongs produced a twofold difference in nest success (33% vs 14%), a higher fledging rate (0.5 vs 0.3 per attempt), and a five-day difference in mean nest survival (18 vs 13 days) (n = 62 nests), although sample sizes for nests in the cull treatment (n = 18) were small and nest predation continued. Although the robin breeding population had not increased one year after the cull, the pool of Yellow Robin recruits in 2001?03, after enhanced fledging success, produced two emigrants to a patch where Yellow Robins had become extinct. Management to assist the conservation of open-nesting woodland birds should address control of currawongs.

QUANTIFYING MALE WOOD THRUSH NEST-ATTENDANCE AND ITS RELATIONSHIP TO NEST SUCCESS

Male Wood Thrushes (Hylocichla mustelina) attend their nests by perching near its rim, a behavior common to many species and presumed to be for the purpose of guarding eggs or young in the nest. We classified nests into two groups based on whether or not we observed an attending male during any nest inspection. We found that nests attended by male Wood Thrushes had higher success rates (i.e., lower predation rates) than unattended nests in Illinois where Blue Jays were a dominant nest predator. In contrast, there was no significant difference in nest success between attended and unattended nests in New York where rodents (mice and chipmunks) and raptors, such as the Sharp-shinned Hawk, were important predators on nests and adults, respectively. Despite differences in risk to adults and nests between the two sites, the frequency of observing attendant males did not differ between sites. In contrast to studies in the literature, the frequency of nest-attendance in the New York population was negatively related to year-to-year variation in chipmunk density, an independent measure of the risk of nest predation. Cuantificación de la Presencia del Macho de Hylocichla mustelina en el Nido y su Relación con el Éxito del Nido Resumen. Los machos de Hylocichla mustelina se posan cerca del borde sus nidos aparentemente con el propósito de vigilar sus huevos o sus crías, lo que representa un comportamiento común en muchas especies. Clasificamos los nidos en dos grupos basados en la presencia o ausencia de un macho durante las inspecciones de los nidos. Encontramos que los nidos que presentaron machos de H. mustelina tuvieron mayores tasas de éxito (i.e., menores tasas de depredación) que los nidos sin machos en Illinois, donde Cyanocitta cristata fue el depredador de nidos dominante. En contraste, no hubo una diferencia significativa en el éxito de los nidos entre los que contaron o no con la presencia de machos en Nueva York, donde los roedores (ratones y ardillas listadas) y las rapaces (como Accipiter striatus) fueron importantes depredadores tanto de nidos como de adultos. A pesar de las diferencias en el riesgo al que están sujetos los adultos y los nidos entre los dos sitios, la frecuencia de observación de presencia de machos no difirió entre los sitios. En contraste con los estudios publicados, la frecuencia de la presencia de machos en los nidos en la población de Nueva York se relacionó negativamente con la variación interanual en la densidad de ardillas listadas, lo que representa una medida independiente del riesgo de depredación de los nidos.

Nest usurpation is an ‘edge effect’ for Carolina chickadees Poecile carolinensis

During 1995–1997, we monitored Carolina chickadee Poecile carolinensis nests in a fragmented forest landscape in northcentral Ohio, USA. Nest success was positively correlated with woodlot area and most nest loss was due to nest destruction by house wrens Troglodytes aedon. During 1998 and 1999, we conducted an experiment in both large (>6.8 ha) and small (<6.8 ha) woodlots in which we gave chickadees a choice of nesting on edges of woodlots (preferred wren habitat) or in the center of woodlots. We found no difference in nest success between large and small woodlots, but regardless of woodlot size, nest success was lower on edges than in the center. In the experiment, 100% of nest loss was due to nest destruction by house wrens. Given a choice, Carolina chickadees preferred to nest centrally more often than on edges. These results suggest that in fragmented landscapes where house wrens are common, nest destruction by house wrens is a major cause of nest failure in the Carolina chickadee. Such edge‐dependent interspecific nest‐site usurpation has not been previously recognized as a potentially important selective factor in nest site selection.

Efficacy of Northern Goshawk Broadcast Surveys in Washington State

Statewide surveys conducted for northern goshawks (Accipiter gentilis) by the Washington Department of Fish and Wildhfe (WDFW) in the early 1990s had relatively low detection rates throughout the state and different rates of detection between easte n (1 bird/55 kn and western Washington (1 bird/174 km To investigate the possibility that survey methods or regional habitat characteristics affected detection rates, we tested broadeast calls at 40 nest stands known to be occupied by nesting northern goshawks. During 439 station visits and 210 trials, we recorded 109 detections, 68% of which were vocalizations. Northern goshawks at 37 of the 40 (93%) occupied territories re detected at least once, including 4 occupied sites that failed. Detectability was eater at successful nests Juvenile northern goshawks were more responsive than adults, which increased detection rates at successful nests by 37% during the postfledging period and accounted for 87% of responses. Logistic regression modeling identified distance of the surveyon to the nest as the only factor correlated with detection rates (P < 0.001). Probability of detecting northern goshawks at occupied stands increased as nests were approached from 400 m (0.20), 250 m (0.25), and 100 in (0.42). Binomial expansion of detection probabilities at a single nest visit found broadcasting to attain ≥90% detections required 5 visits at 100 m, 8 at 250 m, and 10 at 400 m. Because analysis of detection rates by area did not show an effect of vegetation screening, slope, or topography, differences in the relative abundance of northern goshawks from earlier surveys reflect true variation in abundance, differences in nest success, or some combination of both. Results lend more justification for use of broadcast calling for northern goshawk in Pacific Northwest torests and provide a hypothetical model for estimating survey costs as a function of detection probability, trial frequency, and station spacing.

Mate choice in American Redstarts: by territory quality?

We consider the hypothesis that mate choice in American Redstarts (Setophaga ruticilla) depends primarily on features of territories held by males. We test the hypothesis that the territories of yearling males are demonstrably different from and inferior for reproduction to those of adult males. Territories held by the two age-classes in New Brunswick, Canada, were floristically different, but there were also major differences in territorial features in three microgeographic areas, both within each age-group and without regard to age. There were greater differences in nest success between areas than between the age-classes. We detected no differences in immediate nest site features between nests built by the mates of yearling and adult males. There were differences across the three areas in the species of trees used as nest sites, probably reflecting differences in availability. Support for the claim of different reproductive success in relation to quality of territories held by the two age-classes of males is not convincing.

Clutch Size, Reproductive Success, and Organochlorine Contaminants in Atlantic Coast Black-Crowned Night-Herons

Abstract In 1979, we gathered clutch-size and reproductive-success data on Black-crowned Night-Herons (Nycticorax nycticorax) nesting in three New England and two North Carolina colonies. In 1975, we gathered similar data from one of the New England and one of the North Carolina colonies. Latitudinal differences in clutch initiation were not evident. Mean clutch size was larger in the New England than in the North Carolina colonies. Mean clutch size was smaller in late nests from one New England colony studied in both years and another New England colony studied in 1979; seasonal trends in clutch size for other colonies were not found. In 1979, nest success was greater in two New England colonies than in one North Carolina colony. Within-season differences in nest success occurred but were inconsistent among colonies. In the four instances where statistical comparisons could be made, larger clutches were more successful than smaller ones in two colonies; large and small clutches had similar success in two other colonies. One egg was collected from each of several nests in each colony in 1979 for organochlorine contaminant analysis, and the fate of the remaining eggs was recorded. Concentrations of DDE and PCBs did not differ with clutch size; concentrations of PCBs were lower, however, in eggs laid late in the season. Although the data suggest an effect of DDE on hatching success in the northern more contaminated colonies, the impact of environmental contaminants on overall reproductive success appears to be minimal.