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The habitat choice of nest sites by founding queens of leaf‐cutting ants varies with abiotic factors such as temperature, soil density, and soil humidity. In this study, we tested the hypothesis that soil density and moisture affect excavation effort (i.e., excavation period, excavated soil amount, initial nest depth, initial chamber volume, and mortality) in queens of the leaf‐cutting ant Atta sexdens (L.) (Hymenoptera: Formicidae). Queens were placed in experimental areas in three natural soils in Brazil with varying density and moisture content. The excavated soil was collected, dried, and weighed, and digging period, nest depth, chamber volume, and queen mortality were evaluated after nest establishment. In artificially shaded habitats (less dense and more humid soil), the establishment of queens was greater, the period of nest foundation was shorter, and excavated soil amount, nest depth, and volume of the initial chamber were greater than in forest and pasture habitats (denser and drier soils). Also, queen mortality was lower in less dense, more humid soil. This indicates a trade‐off between maximizing the depth of the nest, to increase protection against inadequate environmental conditions, and minimizing energy expenditure during excavation, affecting their survival. [ABSTRACT FROM AUTHOR]

Interspecific competition is expected when two species share resource needs. For example, secondary cavity‐nesting birds may compete vigorously for suitable nest sites both within and among species. However, little is known of whether monogamous species defend more than one nest site on their territory after breeding has begun, and in particular whether they are aggressive against other species. Defending extra nest sites may be adaptive because they may be used for renesting after a failure or to produce a second brood. We studied interactions between a monogamous, resident bird, the great tit Parus major and a migrant, the pied flycatcher Ficedula hypoleuca, providing nest boxes in woodlands in Norway. Agonistic behaviours may be subtle and easily overlooked so we experimentally placed caged male pied flycatchers near nests of great tits and at a dyad of empty nest boxes erected in the territory 25 m away. We filmed interactions between species at 21 sites in the egg‐laying period of the tit, and at 26 nest sites during incubation. Male great tits showed aggression towards the caged flycatcher both at their own nest box and at the nest boxes erected at a distance. We manipulated the external appearance of the nest boxes with painted designs around the entrances but the intensity of aggression at the empty nest boxes did not depend on whether those boxes matched the nest box with the tit nest and was not correlated with tit clutch size. Neither was the intensity of display activity at each nest box by the flycatchers that settled associated with these variables. The results are discussed in relation to hypotheses for nest site choice involving interspecific social learning and aggression. [ABSTRACT FROM AUTHOR]

During a 13‐yr study near Utqiaġvik (formerly Barrow), Alaska, we documented the prevalence of nest reuse in eight arctic‐breeding shorebirds. We evaluated whether nest reuse saved individuals time and energy, enhanced nest survival, or was related to nest density. We documented 208 (6.2%) cases of nest reuse among 3336 nesting attempts. Nest reuse occurred in all years but the first and in all species, with greatest reuse in semipalmated sandpiper (10.9%) and American golden‐plover (10.0%). While most cases of nest reuse occurred with conspecifics, many cases of heterospecific nest reuse were also observed, indicating high niche overlap in nest site preferences among species. We found that individuals reusing old nests may have benefited by nesting earlier, but nest reuse did not generally enhance nest survival. A significant positive relationship was also found between nest reuse and nest density at the community level and for four of the eight species, suggesting high inter‐ or intraspecific competition combined with limited suitable nest sites may force individuals to reuse old nests. Our observations also suggest that upland nesting species may be the most dependent on old nest sites. Preferential development of these sites may therefore have a previously unknown detrimental effect on these species, although further study is needed to better determine the impact of such habitat loss. [ABSTRACT FROM AUTHOR]

Abstract: The globally threatened blue swallow Hirundo atrocaerulea, with <1500 pairs remaining, is an intra‐African migrant, breeding in eight countries in East Africa and Southern Africa, with nonbreeding birds in four countries in East Africa. Blue swallows build an open cup‐shaped nest out of mud and straw in an existing hole in the ground. An updated description of a blue swallow's nest site is that it is a hole in the ground, that faces in a region‐specific direction that maximizes reproductive success, with a roof or overhang or vegetation sufficient to keep the rain off the nest and its contents. Blue swallow breeding success was significantly different between KwaZulu‐Natal and Mpumalanga but, within each province, not between natural and artificial nest sites. Based on the number of fledglings per egg, blue swallow breeding success in Mpumalanga was best in north‐ and west‐facing nest sites, and in KwaZulu‐Natal, breeding success was best in north‐ and east‐facing nest sites. Artificial nest sites should continue to be created for blue swallows that are north to west facing in Mpumalanga (and possibly in Swaziland), and north to east facing in KwaZulu‐Natal. [ABSTRACT FROM AUTHOR]

ABSTRACT Understanding the habitat relationships of rare species is critical to conserving populations and habitats of those species. Nesting habitat is suspected to limit distribution of the threatened Mexican spotted owl ( Strix occidentalis lucida), and may vary among geographic regions. We studied selection of nesting habitat by Mexican spotted owls within their home ranges in the Sacramento Mountains, New Mexico. We compared characteristics of owl nest trees and nest sites to characteristics of randomly located trees and sites at 2 spatial scales: the general nest vicinity and within activity centers used by spotted owls. Owls nested primarily in mixed-conifer forest (92%), and most nested in cavities in trees or snags (48%), or in dwarf mistletoe ( Arceuthobium spp.) witches' brooms (36%). Owl nest trees had greater levels of dwarf mistletoe infection and were larger in diameter than random trees at both of the evaluated spatial scales. Nest trees also were more likely than random trees to be in white fir ( Abies concolor) or Douglas-fir ( Pseudotsuga menziesii), and in trees or snags with broken tops. Differences between owl nest sites and random sites differed with the scale at which we selected random sites, but at both scales examined, owl nest sites had greater canopy cover and more basal area contributed by large trees and white fir than random sites. In addition, most nest sites occurred in drainage bottoms or on the lower 2 thirds of north- or east-facing slopes. Conservation of owl nesting habitat in this area will require retaining forest patches with high canopy cover and large trees containing cavities or large dwarf mistletoe witches' brooms. Locating forest management treatments on ridgetops or the upper third of slopes and/or on south- or west-facing slopes may reduce impacts to owl nesting habitat while simultaneously targeting the drier forest types most in need of restoration. © 2013 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Generalized suitability curves, developed for the spawning habitat of grayling Thymallus thymallus by combining new preference data with information available in the literature, provided optimal ranges for dominant substratum size, water depth and mean water velocity. These were 16–32 mm, 30–40 cm, and 50–60 cm s−1, respectively. Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]