Nest-site Parameters Research Articles

Costs of breeding far away from neighbors: Isolated host nests are more vulnerable to cuckoo parasitism

A series of parasitic and anti-parasitic strategies has evolved during the long-term coevolution between cuckoos and their hosts. The first stage of the arms race is host nest choice by cuckoos, followed by nest defense by hosts. This study examined nest defense strategies of the Oriental reed warbler (Acrocephalus orientalis) in relation to parasitism by the common cuckoo (Cuculus canorus). Attack rate of Oriental reed warblers against common cuckoo dummies was 100% and neighboring individuals participated in 87.1% of such attacks. Furthermore, the number of hosts attacking cuckoo dummies was significantly positively correlated with the number of neighbors at a distance from 40 to 70 m, indicating social anti-parasitic behavior. Analysis of nest-site parameters indicated that the distance to the nearest neighboring unparasitized nest was significantly shorter than that of parasitized nests. Our study demonstrated that isolated nests of Oriental reed warblers with distant neighbors were more vulnerable to common cuckoo parasitism suggesting a cost of breeding far away from neighbors. We hypothesize that cooperative behavior within local populations of Oriental reed warblers can probably be considered as an anti-parasitic strategy developed through long-term coevolution. Choice and parasitism of isolated host nests far away from neighbors may be an adaptive parasitic strategy by common cuckoos to increase the probability of successful parasitism.

Nestling growth and nest success of Gull-billed Tern Gelochelidon nilotica (Aves: Sternidae) in western Iran

The nesting success and nestling growth were studied in a Gull-billed Tern Gelochelidon nilotica Gmelin, 1789 colony located in western Iran, during the 2008 breeding season. The nesting success was modelled in order to assess the effects of various nest-site parameters and nest initiation date. Nestling growth rate, described as body mass, head-bill and tarsus growth per day during the first 10 days of age, was analyzed in relation to brood size and the hatching position of nestlings. Mean daily growth rate of nestlings’ mass (7.82 ± 0.35 g/day) varied in broods of different size but remained independent of nestlings’ hatch order within the brood. Similarly, the growth rate of head-bill length was influenced only by brood size while neither brood size nor hatching position had a significant effect on the wing length growth rate. Nest initiation dates and plant cover around the nests were the most important factors predicting nesting success. As time of breeding period progressed, the rate of nesting success increased. Higher plant cover around the nest also increased the nesting success, probably by hiding the eggs and providing shelter for nestlings thus decreasing predation and mortality rate.

Variations in Nest-Site Parameters in Breeding Waterbirds at Lake Zarivar, Western Iran

Variations in nest-site parameters were studied at Lake Zarivar, Kurdistan Province, Western Iran in 2007 and 2008. This study was applied for six breeding waterbird species: Great-crested Grebe (Podiceps cristatus), Little Grebe (Tachybaptus ruficollis), Moorhen (Gallinula chloropus), Coot (Fulica atra), Water Rail (Rallus aquaticus) and Whiskered Tern (Chlidonias hybrida). A total of 205 nest-sites were studied in terms of five environmental factors: vegetation density and height, water depth, distance to open water, as well as distance to the nearest nest of the conspecific species were measured. Great-crested Grebes selected areas of deeper waters, possibly to increase feeding efficiency. All species were directly dependent on water for nesting, except for the Water Rail, which established its nest in muddy areas with higher vegetation density and height. Nests were at a higher density for the Whiskered Terns than in other species. Overall, mean water depth at nesting sites was lower in the 2008 breeding season and total breeding population of waterbirds decreased. Evaluating and monitoring of habitat quality of breeding species urges conservation measures with regard to transformations occurring at this freshwater lake ecosystem.

Flight Distances of Incubating Common BuzzardsButeo buteoare Independent of Human Disturbance

In a Danish landscape with relatively high (134/km2) but variable human density, 86% of 213 incubating Common Buzzards Buteo buteo flushed from the nest at distances of 0–200 m in response to a person approaching on foot. Flight distances were not conditional on nest site parameters despite considerable variation in human disturbance variables, lending no support for the hypothesis that Common Buzzards are more tolerant of humans in disturbed locations.

Nest-Site Selection by Marsh Harrier (Circus Aeruginosus) in the Shore Belt of Helophytes on Large Lakes

Nest-site selection by Marsh Harrier (Circus aeruginosus) was investigated on Lakes Meteliai and Obelija in 1983–1986 and Lake Žaltytis in 1984–1986 in southern Lithuania. Fifty five breeding pairs were detected and 49 nests (89.1%) were found. With regard to the potential breeding habitat, Lakes Meteliai and Žaltytis represented extreme structural types, whereas Lake Obelija – the intermediate type. Despite these differences, most nest-site parameters of the three lakes did not differ or differed slightly. The most similar was the depth. Only the most dissimilar lakes differed according to nest-site vegetation density and height, the latter varied according to the dominant helophytic species on the lake. Distances from nests to water and shore were not statistically significant – nests were built in the middle of the emergent vegetation belt. While selecting nest-sites, pairs gave preference to patches larger in area and diameter. Nest-site selection peculiarities are explained by birds’ balanced efforts...

Nest-Site Characteristics and Nesting Success of the Greater Pewee in Arizona

Nest-Site Characteristics and Nesting Success of the Greater Pewee in Arizona

Spawning success in the damselfishAmblyglyphidodon leucogaster: the influence of eggs in the nest

Spawning success of males and its correlates were investigated in a natural colony of whitebelly damselfish,A. leucogaster(Pomacentridae), to explore the criteria that females use in choosing mates. The mating success of individual males was variable, with some males acquiring as few as 5000 eggs and others as many as 450000 eggs during a breeding season. Male spawning success was not correlated with body size, territory size, nest site parameters or parental care behaviour. Egg hatching success was not related to either male size or egg clutch size, and all males were capable of rearing eggs to hatching. The temporal sequence of choices by females indicated non-independent choice by females, such that males chosen by females on the first spawn of the day were also chosen by females that spawned later in the day. Field observations indicated that, in the absence of male courtship, females preferentially visited males that had eggs in their nest site. Males that had recently mated were preferred by females over those males with either late-stage eggs or no eggs in the nest. This female preference did not appear to be related to increased paternal care or egg clutch survival. Given that the mating system is promiscuous and non-resource based, and that there appears to be little difference among males in body size, females may be mating non-independently by mimicking the choice of other females.

Forest Structural Characteristics of Accipiter Nesting Habitat: Is There an Allometric Relationship?

In montane forests of the western United States, a general correlation of Accipiter body size and scaling of the vegetation component of nesting sites and nest trees used by sympatric Accipiter species has been reported. We evaluated this pattern with vegetation data collected at Northern Goshawk (Accipiter gentilis), Cooper's Hawk (A. cooperii), and Sharp-shinned Hawk (A. striatus) nest sites in the Jemez Mountains and Pajarito Plateau of north-central New Mexico. We selected habitat variables at the nest tree and nest site scale that would allow us to evaluate the prediction that accipiters use nesting habitat in which their body size is positively correlated with tree size and tree spacing, and inversely correlated with tree density, basal area, and percent canopy closure. At the nest-site level, density of larger diameter trees should be positively correlated with body size, and density of smaller diameter trees should be inversely correlated with body size. Our results suggest that nest tree height and diameter support body size predictions about nesting habitat for accipiter hawks. None of the nest-site parameters measured in this study supported the body size predictions due to a large amount of intra-specific variation. As a result ofthis variation, it was difficult to differentiate between Cooper's Hawk and Northern Goshawk nest sites for most site variables. These results suggest there is a correlation between accipiter size and nest tree size, but that a correlation between nest site structural size and accipiter body size may not be a widespread phenomenon for all vegetation variables for all three species. Many commonly measured forest stand structural characteristics such as basal area and total tree densities may not be adequate for predicting suitable accipiter nesting habitat in all areas, particularly in the absence of comparisons with available habitat.

NEST-SITE SELECTION BY ROSEATE TERNS AND COMMON TERNS IN THE AZORES

Nest-site characteristics of Roseate Terns (Sterna dougallii) and Common Terns (S. hirundo) in mixed and unmixed colonies were examined at a number of sites in the Azores archipelago using discriminant analysis. Colonies were stratified and points located in a systematic way. Physical parameters, nearest-neighbor distance, vegetation cover, and density of nests were measured. Measured nest-site parameters were compared between species and with habitat points selected in the colony. Significant interspecific differences in nesting sites were found. Roseate Terns nested in areas with high relief and/or tall vegetation and with higher nesting densities. Common Terns selected more-open areas. There was considerable variability in nest-site selection of both tern species among colonies. Roseate Terns were more specialized as their nest sites differed more significantly than those of Common Terns from the available habitats. In contrast to findings of studies in North America, nest con- cealment by Roseate Terns did not influence hatching success. Competition may be important in nest resource partitioning in individual mixed colonies depending on colony size and habitat structure. The need to maintain/create optimal nesting areas for Roseate Terns is stressed. As habitat descriminators varied greatly between colonies, management should be planned on a colony-by-colony basis. Received 15 March 1994, accepted 15 May 1994.

Nest site selection in Norwegian woodpeckers

The nest site selection of seven Norwegian woodpeckers, Dryocopus martius, Picus viridis, P. canus, Picoides tridactylus, Dendrocopos leucotos, D. major and D. minor, was compared. The following parameters were measured at the nesting tree: forest type, tree species, the tree's “degree of decay”, the height of the tree, the hole's height above the ground, the stem's diameter at the hole and 0.5 m above the ground, earlier holes in the stem, and whether the tree was broken or not. Several differences between species were found in forest type and tree species. The use of weakened and dead nesting trees tended to increase with decreasing size of the bird. The following parameters usually decreased with decreasing size of the species: the height of the tree and of the nesting hole, and the stem's diameter at the hole and near the ground. Overlap in nest site parameters was calculated for four species, D. martius, P. viridis, D. major and D. minor, common nesters in Populus tremula. Overlap between D. minor and the other three species was low, whereas considerable overlap was found between D. martius and P. viridis. Both species prefer large, old Populus tremula trees.

Nesting Phenology and Competition for Nest Sites among Red-Headed and Red-Bellied Woodpeckers and European Starlings

Nesting Phenology and Competition for Nest Sites among Red-Headed and Red-Bellied Woodpeckers and European Starlings

Reproductive Ecology of Female Dusky Salamanders, Desmognathus fuscus (Plethodontidae), in the Southern Appalachians

Desmognathusfuscus is a plethodontid salamander that inhabits streambanks throughout eastern North America. Because of its habitat affinities, egg clutches and brooding females may be susceptible to mortality from several sources. These include predation by larger plethodontids or snakes that dwell in stream margins, flooding during summer storms, or desiccation. Females in a Tennessee population studied from 1983-85 reproduced on an annual cycle. Fecundity was significantly correlated with female snout-vent length. Most females nested in the streambank beneath clumps of moss, although some animals used rocks or rotting logs as cover objects. Oviposition usually occurred in July or Aug.; the duration of egg brooding was 47.08 ? 17.59 d. Reproductive success averaged over all nests varied among years, ranged from 24.3-49.3%, and was not significantly related to female size, the phenology of oviposition, or nest site parameters. Within most successful nests, at least 70% of the eggs present when the clutch was discovered actually hatched. Among these nests, the fraction of eggs hatched by larger females tended to be higher than the fraction of eggs hatched by small females. Egg mortality probably was caused by predation, rather than by flooding or desiccation. These results lend support to the hypothesis that predation may restrict the abundance of Desmognathus species.

Harem size, territory quality, and reproductive success in the redwinged blackbird (Agelaius phoeniceus)

The relationships between harem size, territory size, nest site suitability, and fledging success were studied for a breeding population of redwinged blackbirds (Agelaius phoeniceus). Reproductive success was correlated negatively with female breeding density within territories and positively with territory quality as determined from nest site parameters. Harem size was not correlated with differences in either territory area or quality. From these results we suggest that some females were attracted to nest in territories in which their chances of successful reproduction were lower than if they had chosen other available territories. To explain the selective advantage of such choices, we postulate that females were choosing mates which would enhance their ultimate fitness rather than their immediate reproductive success.