Availability Of Nest Sites Research Articles

Nest site lottery revisited: towards a mechanistic model of population growth suppressed by the availability of nest sites

In the “nest site lottery” mechanism, newborns form a pool of candidates and randomly drawn candidates replace the dead adults in their nest sites. However, the selection process has only been analyzed under the assumption of an equilibrium population size. In this study, we extend this model to cases where the population size is not at an equilibrium, which yields a simplified (but fully mechanistic) biphasic population growth model, where the suppression of growth is driven only by the availability of free nest sites for newborns. This new model is free of the inconsistency found in the classical single phase models (such as the logistic model), where the number of recruited newborns can exceed the number of free nest sites. We analyzed the stability of the stationary density surfaces and the selection mechanisms for individual strategies described by different vital rates, which are implied by the new model.

Patterns and mechanisms of invasive plant impacts on North American birds: a systematic review

Understanding how invasive plants affect biodiversity is a crucial conservation need. Numerous studies examine impacts of invasions on birds, but trends in these effects have not been synthesized. We reviewed 128 studies from North America to quantify the frequency of positive, negative, and neutral (non-significant) effects of invasive plants on avian ecology, and then evaluated support for proposed mechanisms of impacts. Our frequency-based approach enabled us to draw value from the full breadth of available literature, including articles that do not provide information necessary for meta-analyses and articles examining understudied phenomena. Total avian abundance and prevalence of individual bird species were usually unaffected by invasion, with 48.9 and 57.2% of tests showing neutral results, respectively. Avian richness decreased with invasion in 41.3% of tests. Although birds often preferred nesting in invasive vegetation (45.0% of tests), effects on nest survival were typically neutral (57.9%). Multiple metrics (e.g. body condition, fledgling survival) have received scant attention. Some of the patterns we highlight differ across ecological contexts, emphasizing the need to understand impact mechanisms. Several studies have directly linked invasion impacts to altered nest-site availability, habitat heterogeneity, and food supplies. There is mixed evidence that plant architecture impacts nest-site selection and nest predation. Our review highlights the nonuniform consequences of biological invasions. The high frequency of reported neutral effects suggests that invasions often have minimal impacts on birds, but positive and negative impacts certainly can arise. Managers considering eradicating invasive plants for avian conservation should monitor impacts locally to determine whether eradication will be beneficial.

Effects of Habitat Fragmentation on the Nesting Dynamics of Desert Bees

Anthropogenic changes in land use and habitat fragmentation are thought to be greater drivers of declines in the abundance and species richness of pollinating insects such as bees (Hymenoptera: Apiformes) than agricultural intensification and pesticide use. Yet, few studies have examined how habitat fragmentation by urbanization affects pollinator nesting dynamics. We investigated the nesting dynamics of native solitary bee species that inhabit fragments of Sonoran Desert in Tucson, AZ. Specifically, we compared floral densities, nest completion, and nest attack rates of cavity-nesting bees in large (>2 ha) and small (<0.5 ha) fragments. In small fragments, where resource density was high, more nests were occupied and females responded by provisioning offspring more quickly than in larger fragments where resource density was low. However, nests in small fragments were more likely to be attacked by natural enemies than those in large fragments. In this desert system, habitat size, the most-often used metric for examination of how pollinators respond to habitat fragmentation, affects nesting dynamics and demographics through its interactions with nest-site availability, abundance of floral resources, and natural enemy attack. As landscape fragmentation increases, pollinator conservation should not only consider food sources but also nesting requirements and interactions with natural enemies.

Do hyperabundant Arctic-nesting geese pose a problem for sympatric species?

Arctic-breeding geese are at record high population levels and are causing significant changes to some of their breeding and staging habitats. These changes could influence sympatric wildlife, but the nature and strength of these effects are unknown. Here, we review the interactions between geese and sympatric species and propose future research that could help to fill important knowledge gaps. We suggest that geese may be indirectly affecting other species through changes to nesting habitat, prey availability, and predator–prey interactions. Many ground-nesting Arctic birds prefer vegetated wet tundra habitats that offer concealed nest sites; areas also heavily used by breeding and staging geese. Where goose foraging exceeds the capacity of the plants to regenerate, habitats have shorter graminoids and more exposed substrate, potentially reducing the availability of concealed nest sites for other birds. Studies have documented local reductions in the abundance of these concealed-nesting species, such as shorebirds. Despite the nutrient enrichment contributed by goose feces, habitats heavily altered by geese have also been shown to host a reduced diversity and abundance of some invertebrate groups. In contrast, generalist predators show positive functional and numerical responses to the presence of breeding geese. Therefore, the risk of predation for alternative or incidental prey (e.g., lemmings or small bird nests) is likely elevated within or near breeding colonies. Studies have demonstrated a reduced abundance of small mammals in areas heavily used by geese, but it is unknown whether this is related to shared predators or habitat alteration. Sympatric wildlife could be further affected through higher stress-levels, altered body condition, or other physiological effects, but there is currently no evidence to demonstrate such impacts. Few studies have explored the potential effects of geese at larger spatial scales, but we suggest that hyperabundant geese could result in regional declines in the abundance and diversity of shorebirds and passerines. We recommend coordinated studies across multiple regions to quantify nesting habitat, arthropod communities, and predator–prey interactions in response to nearby goose colonies. To align with current multispecies approaches to conservation, adequate knowledge of the potential effects of hyperabundant goose populations on other wildlife should be a priority.

Grey HeronArdea cinereaProductivity in Relation to Habitat Features and Different Spatial Scales

Life history traits of birds like survival or reproduction are strongly related to habitat features which affect food and nest-site availability. However, impact of habitat variables on life-history traits, which may be scale-dependent is barely studied. We investigated the relationships between landscape features and productivity (expressed as the number of 21–38 day old chicks per nest) of a colonial waterbird, the Grey Heron Ardea cinerea in northern Poland. In 2014 we analysed the landscape features (hydrographic features, habitat area, habitat patchiness and distances to the nearest water bodies, coastline, rivers/canals, buildings and roads) around the six colonies. We analysed all those features in four spatial scales around the colony: close proximity of the colony (0–1 km), closer foraging grounds (0–10 km), far foraging grounds (0–20 km) and far foraging grounds excluding close foraging areas and proximity of the colony (10–20 km). The differences in productivity among the colonies was not significant in the studied year (mean number of chicks ± SD: 3.57 ± 0.52). At each spatial scale excluding 10–20 km radius, Grey Heron productivity increased with increasing habitat heterogeneity and decreased with increasing length of rivers/canals and area of pastures. The results of this study indicate that the spatial scale of 0–10 km was the best to indicate relationships between landscape features and productivity in herons. Distance to the nearest river/canal banks, buildings and roads were related positively to productivity. Our study revealed the importance of landscape complexity of aquatic and terrestrial habitats for the Grey Heron productivity.

The canary in the coalmine; bee declines as an indicator of environmental health.

Bee declines have received much attention of late, but there is considerable debate and confusion as to the extent, significance and causes of declines. In part, this reflects conflation of data for domestic honeybees, numbers of which are largely driven by economic factors, with those for wild bees, many of which have undergone marked range contractions but for the majority of which we have no good data on population size. There is no doubt that bees are subject to numerous pressures in the modern world. The abundance and diversity of flowers has declined along with availability of suitable nest sites, bees are chronically exposed to cocktails of agrochemicals, and they are simultaneously exposed to novel parasites and pathogens accidentally spread by humans. Climate change is likely to exacerbate these problems in the future, particularly for cool- climate specialists such as bumblebees. Stressors do not act in isolation; for example pesticide exposure can impair both detoxification mechanisms and immune responses, rendering bees more susceptible to parasites. It seems certain that chronic exposure to multiple, interacting stressors is driving honeybee colony losses and declines of wild pollinators. Bees have a high profile and so their travails attract attention, but these same stressors undoubtedly bear upon other wild organisms, many of which are not monitored and have few champions. Those wild insects for which we do have population data (notably butterflies and moths) are overwhelmingly also in decline. We argue that bee declines are indicators of pervasive and ongoing environmental damage that is likely to impact broadly on biodiversity and the ecosystem services it provides.

Effects of intense wildfires on the nesting ecology of oviparous montane lizards

In midsummer 2002–2003, intense wildfires raged through the Brindabella Range of south-eastern Australia, including sites where we have studied the ecology of scincid lizards (especially Bassiana duperreyi) for decades. Data-loggers measured the thermal regimes experienced by eggs during these fires (revealing lethally high temperatures in nests under logs in the forest but minimal effect in nests under rocks in clearings). Eggs from forest-clearing nests hatched successfully. Reproductive output of lizards in one area was reduced in the years post-fire (perhaps because of inadequate food [insect] abundance to fuel female reproduction) but soon recovered. The fires reduced vegetation density and thus increased the availability of sun-exposed rocks that serve as potential nest sites. However, the magnitude and duration of these effects differed among sites. Five years after these intense fires, canopy openness (and thus, sunlight penetration to create thermally suitable nest sites) was indistinguishable from pre-fire conditions. Our data reveal strong spatial heterogeneity both in the immediate effects of fire on lizard reproduction and in longer-term post-fire changes in habitat quality. Surprisingly, these intense wildfires had only transitory and local effects on nest-site availability for the heliothermic lizards that we study, but impacts likely were more severe on sympatric taxa that depend upon moist cool microhabitats.

Site preferences for nesting by birds in an educational institution campus in Bengaluru, Karnataka, South India.

Wildlife conservation in urban habitats is increasingly important due to current urbanization trends. Studying birds in urban landscapes and pointing out the importance of their management and conservation are the needs of the day. Every species has certain habitat requirements for successful nesting and breeding. The increase in anthropogenic activities and the disappearance of native tree populations has raised concerns on avian populations and its nesting behavior. In this study, we observed the nesting success of urban birds in the campus. It is found that nesting failure is not predicted by the density of adult birds. These findings suggest that nesting success determined by nest site availability may drive the distribution of avian species in the urban habitat. The abundance of urban bird species nesting in Christ University campus was studied and the need for planting trees that are more conducive for nesting by birds is recommended.

Population and Nesting Records of House Sparrow &lt;i&gt;Passer domesticus &lt;/i&gt; in Yellampet, Nizamabad District, Telangana, India

We studied the population and nesting records of House Sparrow Passer domesticus during winter in Yellampet village, Telangana. The ecological density of House Sparrow was investigated using fixed width transects. The density of sparrow vary from 15 to 335 per hectare in different transects. Bonferroni confidence interval was used to know the preference of location types i.e., houses, shops and hotels for foraging and nesting. Shops were used significantly more than expected according to availability of nest sites and also for foraging. A total of 81 active nests were recorded. The present study shows that a handful breeding population of House Sparrow harboring in Yellampet village.

Population and Nesting Records of House Sparrow &lt;i&gt;Passer domesticus &lt;/i&gt; in Yellampet, Nizamabad District, Telangana, India

We studied the population and nesting records of House Sparrow Passer domesticus during winter in Yellampet village, Telangana. The ecological density of House Sparrow was investigated using fixed width transects. The density of sparrow vary from 15 to 335 per hectare in different transects. Bonferroni confidence interval was used to know the preference of location types i.e., houses, shops and hotels for foraging and nesting. Shops were used significantly more than expected according to availability of nest sites and also for foraging. A total of 81 active nests were recorded. The present study shows that a handful breeding population of House Sparrow harboring in Yellampet village.

Light grazing of saltmarshes increases the availability of nest sites for Common Redshank Tringa totanus, but reduces their quality

The breeding population of Common Redshank Tringa totanus on British saltmarshes has reduced by >50% since 1985, with declines linked to changes in grazing management. Conservation initiatives have encouraged low-intensity grazing of 0.5 cattle ha−1y−1 but even light grazing can lead to high rates of nest mortality. To avoid predators, Redshank nest in patches of tall vegetation, but the effects of grazing on the availability and quality of habitat selected by Redshank remain unclear. We investigated Redshank nest site selection in relation to cattle grazing and asked (a) which nest vegetation conditions do Redshank select and (b) does grazing limit the availability of higher quality nest sites? We characterised vegetation height and composition at nests and control locations on six saltmarshes grazed between 0 and 0.55 cattle ha−1y−1, which falls within or near the UK Environment Agency definition of light grazing. Redshank selected nest locations in the tallest vegetation available (26±13cm with no grazing), but grazing limited the availability of such tall vegetation (11±7cm at 0.55 cattle ha−1y−1). However, Redshank also selected nest locations dominated by the grass Festuca rubra, which increased with higher livestock densities. By causing Redshank to nest in shorter vegetation, but with more of their preferred grass species, grazing presented a trade-off for Redshank. As previous work has shown that nesting in shorter vegetation results in higher nest predation rates, results of this study suggest that even light conservation grazing can result in Redshank nesting in lower quality habitat. Reducing saltmarsh grazing levels below 0.55 cattle ha−1y−1 may therefore increase Redshank populations by maintaining a vegetation structure with patches of F. rubra but with longer sward heights for nesting.

The Relative Abundance of Invasive House Sparrows (Passer domesticus) in an Urban Environment in South Africa is Determined by Land Use

The House Sparrow, Passer domesticus, is invasive in many areas of the world, but is listed as a species of conservation concern in parts of its native range. This study assessed the effect of land-use type on the relative abundance of House Sparrows in Pietermaritzburg, South Africa, an urban area where they are invasive. It was predicted that House Sparrows in an urban environment would be more abundant at shopping malls compared with other habitats. Spot counts were done at shopping malls, schools, factories and suburban gardens throughout the year. House Sparrows were recorded frequently at shopping malls and rarely in suburban gardens. Type of urban land use appears to determine food and possibly nest site availability. This in turn affects the density, relative abundance, and distribution of House Sparrows. There appears no need to regulate this urban House Sparrow population because it has different feeding and breeding requirements to native birds, is not predatory, and is largely restricted to heavily transformed landscapes.

Nest Site Characteristics of the Newly Established Eurasian MagpiePica picaPopulation in Hokkaido, Japan

Abstract Nest site availability is an important factor promoting the establishment of introduced bird species. Since the 1990s, the Eurasian Magpie Pica pica has colonized an area of southwestern Hokkaido, in northern Japan. In this study, we investigated the characteristics of magpie nest sites in Tomakomai, Hokkaido, at multiple spatial scales: home range, territory, and microhabitat, in order to understand the environmental factors that have supported the magpie's successful establishment. We found 67 nests (49 on trees; 18 on artificial structures) in May 2011. We analysed nest locations and surrounding land use, using nest presence/absence data and a logistic regression analysis, in order to reveal preferable environments for magpies. At the home range scale, the urban environment positively influenced nest presence. We also revealed by territory scale analysis that magpies used tree-dense patches when nesting on trees, while magpies built nests on artificial structures when tree density was relative...

Moving northward: comparison of the foraging effort of Magellanic penguins from three colonies of northern Patagonia

The Magellanic penguin Spheniscus magellanicus has recently colonized two new coastal sites (Islote Lobos and El Pedral), increasing the number of colonies in northern Patagonia, Argentina. Assuming foraging parameters during the breeding season to be valid short-term indicators of population health, we studied several foraging parameters of penguins from the two new established sites and from an older and well-established colony (Punta Norte) also localized in the north of Patagonia. Penguins from the recently formed colonies performed shorter foraging trips and visited waters closer to their colony than birds from Punta Norte, with penguins from Punta Norte spending almost twice the time at sea spent by penguins from El Pedral. Penguins from Punta Norte also spent more time underwater, spent a higher proportion of the complete diving cycle searching for prey, performed more wiggles (indicative of prey capture) and had fewer estimated prey captures per unit time underwater than penguins from Islote Lobos and El Pedral. This information suggests that, given no limitations on nest-site availability and no prevalence of predators, the good foraging conditions around El Pedral and Islote Lobos may be implicated in the increase in these two relatively new colonies.

Diversity of great gray owl nest sites and nesting habitats in California

The great gray owl (Strix nebulosa) is listed by the state of California as endangered, with a population estimate of fewer than 300 individuals in the state. Nest-site availability has been suggested as a limiting factor for population growth in California, but information on nest types and nesting habitat has been based on a small number of nests that may not fully represent the variety of conditions used by the species. We collated all known nesting records in the Sierra Nevada mountains of California since 1973 (n=56) and then visited 47 of the nest sites to characterize habitat and compare them with paired reference sites. Great gray owls used a diversity of trees (8 species) and nest types. Although great gray owls in California are considered conifer-forest specialists, 30% of nests were in oak trees and 21% were below 1,000 m, which loosely corresponds to the lower conifer-zone limit. Across all elevations and tree species, degree of deterioration was the most important factor differentiating nest trees from paired reference trees at the same meadow, with nest trees being significantly more decayed. Nest trees (mean dbh = 100.5 ± SD 30.3 cm) were also significantly larger than reference trees. Canopy cover within 50m of nest trees (x = 85.1 ± 16.4%) was significantly greater at nest sites than at reference sites. At higher elevations, most nests were within 250m of a meadow edge, but at lower elevations, 31% of nests were >750m from the closest meadow. Based on these findings, we suggest that managers trying to promote great gray owl nesting maintain 4 or more large (100-cm dbh) snags per hectare in dense forests, especially near meadows. We also recommend increasing great gray owl survey effort in habitats and areas that may have been inadequately surveyed in the past. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Simulations of wood duck recruitment from nest boxes in Mississippi and Alabama

Since the early 20th century, wildlife managers have deployed artificial nesting structures for wood ducks (Aix sponsa) to increase availability of nest sites and local reproduction of the species. However, knowledge is lacking of the effects of nest structure size (i.e., large vs. small; Stephens et al. 1998) and reproductive data (e.g., clutch size, hatch date, duckling survival) on recruitment of wood ducks. We used stochastic simulation analyses to predict recruitment of wood ducks into late summer by analyzing data from a 6-year study of box-nesting wood ducks, and 4-year (Mississippi) and 2-year (Alabama) studies of radio- marked female wood ducks and their ducklings. Our index of recruitment was the number of radio-marked ducklings per nest box that survived until 1 September. Ducklings hatched after 1 June exhibited a 30-day survival probability of 0.29, which was nearly 3 times greater than those hatched before 1 June. In east-central Mississippi, 68% and 65% of total wood duck recruits from large and small boxes, respectively, were hatched and reared from June to August. In western Mississippi, 91% of recruits from each box size also were hatched and reared from June to August. Mean number of wood duck recruits produced from large boxes was greater than small boxes at each study site; each large box in western Mississippi produced approximately 4 recruits on average, whereas small boxes in east-central Mississippi produced approximately 1 recruit. Wood duck recruits in our study resulted primarily from late spring and summer hatched birds in contrast to most Nearctic ducks with adaptive, early nesting to promote recruitment. In Mississippi and similar southern environments, we recommend use of large boxes and cleaning boxes around 1 May after completion of initial nests, and emphasize the importance of late spring and summer duckling production to wood duck recruitment. © 2015 The Wildlife Society.

White-rumped swallows prospect while they are actively nesting

Nest prospecting, that is, visiting potential future nest sites, may be a widespread bird behavior. Here we describe apparent prospecting while nesting by white-rumped swallows (Hirundinidae, Aves). In southern Brazil, birds tagged with passive-integrated transponders (PIT-tags) and breeding in nest boxes with PIT-tag readers: (1) often visited nest boxes that were in use by apparently unrelated birds (54 % of nests were visited at least once), (2) visited other boxes while caring for their own nestlings, (3) tended to have smaller broods than birds that were not recorded visiting, and (4) did not have a preference for any particular box. These patterns do not indicate any clear explanation for nest visiting, but they do show that prospecting is done by floaters (non-breeders) as well as actively breeding individuals. We suggest that these visits occur when time is available and that visitors may be assessing the availability of future nest sites.

Survival and Movements of Post-Fledging American Kestrels Hatched from Nest Boxes

Abstract Population declines of cavity-nesting birds are being recorded worldwide with degraded habitat, reduced prey availability, and limited nest-site availability implicated as potential causal factors for declines. A possible aid for avian species limited by breeding-site availability is the construction of nest boxes. Although nest boxes are commonly used for Falco sparverius (American Kestrels), little is known about the survival of young from fledging to the onset of migration. Using radiotelemetry, we recorded post-fledging survival and movement of 11 juvenile American Kestrels in northeastern Connecticut from June to September 2013. We used the Kaplan-Meier procedure, adjusted for staggered entry of individuals over time, to estimate daily survival at 0.270 (95% CI 0.01, 0.53) at the onset of migration. Causes of mortality included predation (n = 4 American Kestrels), exposure (n = 2), and unknown (n = 1). During the post-fledging period, the farthest net distance that we recorded for an America...

The density of feral honey bee (Apis mellifera) colonies in South East Australia is greater in undisturbed than in disturbed habitats

Apis mellifera is an important pollinator but is sometimes associated with adverse effects on natural ecosystems. We surveyed pairs of disturbed and undisturbed sites across three biomes in South East Australia. We used pheromone lures to trap drones, genotyped the drones to infer the number of colonies within flight range and then estimated colony densities using synthetic sampling distributions. Estimated colony densities ranged from 0.1 to 1.5 colonies km−2 and significantly lower in agricultural land relative to national parks. We suggest that colony density may be lower in disturbed than ‘natural’ areas due to the reduced availability of nest sites and possibly pesticide usage. Because the number of colonies recommended for adequate pollination is 100–1000 colonies km−2, there are insufficient bees to provide optimal crop pollination in the areas we surveyed.

Insectivorous and open-cup nester bird species suffer the most from urbanization

Capsule Urbanization effects in an Eastern European city depend on feeding and breeding traits of bird communities with stronger negative effects on more specialized traits.Aims To assess how urbanization affects feeding and breeding traits of bird communities in Cluj (Romania).Methods Based on a stratified random sampling we selected 61 study squares of 200 × 200 m for bird surveys representing the following habitats: suburban, residential and apartment complex (representing an increasing urbanization gradient). We carried out bird censuses in both breeding and wintering seasons. The observed bird species were classified according to their feeding guilds and nesting sites.Results Insectivorous and open-cup nesting species were most abundant in suburban areas. Omnivorous species richness was not related to urbanization gradient. Species showed similar patterns of distribution during breeding and winter with respect to feeding habits. However, in case of nesting preferences, species richness of cavity nesters increased with urbanization gradient in winter, but decreased in the breeding season.Conclusions Food and nesting site availability are key drivers in limiting more specialist species in utilizing city centres. Future studies should assess the effect of how green areas can counteract such negative effects of increasing urbanization in the context of such specialist trait limitations.