Habitat selection of nesting and fledgling salt marsh songbirds in northeast Florida

Understanding habitat selection by breeding birds and their newly fledged young can be an essential aspect of the conservation of vulnerable species. During 2015–2017, we examined nest site selection of Worthington's marsh wren (Cistothorus palustris griseus) and MacGillivray's seaside sparrow (Ammospiza maritima macgillivraii), and fledgling habitat use by Worthington's marsh wren, 2 imperiled species in northeast Florida, USA. We compared vegetation at unused points to vegetation at nests of both subspecies and at locations used by radio-tagged marsh wren fledglings. Vegetation was taller and stem counts were greater at nest sites compared to unused points. Worthington's marsh wrens also used nest sites with a greater proportion of tall-form smooth cordgrass (Spartina alterniflora) than was observed at unused points. Worthington's marsh wren fledglings also used locations with taller, denser vegetation, but vegetation use changed with fledgling age and tidal stage; older fledglings more frequently used areas with short-form smooth cordgrass and bare ground (and more so during low tides). In contrast, so few nests and nestlings were in black needlerush (Juncus roemerianus) that we could not consider it in our analysis despite its prevalence within our study sites. Our results indicate that tall, dense cordgrass is an important habitat component for these subspecies during the nesting and fledgling life stages in southeastern Atlantic salt marshes.     

A nondestructive method for estimating the age of Clapper Rail eggs

ABSTRACT.   Estimates of nest survival rate are often based on the assumption that the rate is constant during the nest cycle. Because violating this assumption can generate biased estimates, determining the age of a nest is important. For precocial marsh birds, including Clapper Rails ( Rallus longirostris ), current estimates of nest survival do not take this source of bias into account because a standardized, nondestructive method for aging eggs in not available. We developed a nondestructive flotation technique using known-age nests that can be used to estimate the projected hatch date of Clapper Rail eggs within 3 d of the actual hatch date. This precision is limited in part due to variance in the length of incubation between nests and the common occurrence of asynchronous hatching. However, for investigators assessing the fate of Clapper Rail nests, our technique provides an effective and nondestructive method for projecting the hatch date of Clapper Rail eggs, and will facilitate unbiased estimates of nest survival rates.     

Effects of a habitat-altering invader on nesting sparrows: An ecological trap?

Many invading species impact native species through predation, parasitism or competition, while others affect natives indirectly by restructuring their habitat. How invasive plants affect native animals, and to what extent native animals respond to changes in their habitat and the novel selection pressures that follow, is not well known. We investigated the impacts of a habitat-altering invader, the Atlantic cordgrass Spartina alterniflora, on the nesting success of Alameda song sparrows (Melospiza melodia pusillula), a California Species of Special Concern, in tidal marshes in three sites in San Francisco Bay. Date of laying was the most influential factor in determining daily survival rate of nests, but whether the nest was placed in exotic Spartina was the most important ecological variable. Nests placed in exotic Spartina had a success rate that was 30% lower than those placed in native vegetation. Nests in exotic Spartina were significantly more likely to fail due to tidal flooding than were nests placed in native vegetation, because the densest stands of exotic Spartina occurred at significantly lower elevations relative to the tides. Our results suggest that exotic Spartina may be an ecological trap for song sparrows in San Francisco Bay, attracting birds to nest sites that are often destroyed by tidal flooding.     

Tidal‐flow restoration provides little nesting habitat for a globally vulnerable saltmarsh bird

Tidal marshes are among the most threatened habitats on Earth because of their limited natural extent, a long history of human drainage and modification, and anticipated future sea‐level rise. Tidal marshes also provide services to humans and support species of high conservation interest. Consequently, millions of dollars have been spent on tidal marsh restoration throughout North America. Southern New England has a long history of tidal marsh restorations, often focused on removal of the invasive plant Phragmites australis. Working in 18 Connecticut marshes, we examined the bird community in 21 plots in restoration sites and 19 plots in reference sites. Restoration plots were divided into those in marshes where management involved restoring tidal flow and those where direct Phragmites control (e.g. cutting, herbicide) was used. Saltmarsh sparrows Ammodramus caudacutus, which are considered globally vulnerable to extinction, were less common where tidal flow had been restored than at reference sites and nested in only one of 14 tidal‐flow restoration plots. No abundance differences were found for large wading birds, willets Tringa semipalmata, or seaside sparrows Ammodramus maritimus. Vegetation at sites where tidal flow had been restored showed characteristics typical of lower‐elevation marsh, which is unsuitable for nesting saltmarsh sparrows. We conclude that, although tidal‐flow restorations in Connecticut control Phragmites and restore native saltmarsh vegetation, they produce conditions that are largely unsuitable for one of the highest conservation priority species found in eastern U.S. salt marshes.     

Breeding habitat and nest‐site selection by an obligatory “nest‐cleptoparasite”, the Amur Falcon Falco amurensis

The selection of a nest site is crucial for successful reproduction of birds. Animals which re‐use or occupy nest sites constructed by other species often have limited choice. Little is known about the criteria of nest‐stealing species to choose suitable nesting sites and habitats. Here, we analyze breeding‐site selection of an obligatory “nest‐cleptoparasite”, the Amur Falcon Falco amurensis. We collected data on nest sites at Muraviovka Park in the Russian Far East, where the species breeds exclusively in nests of the Eurasian Magpie Pica pica. We sampled 117 Eurasian Magpie nests, 38 of which were occupied by Amur Falcons. Nest‐specific variables were assessed, and a recently developed habitat classification map was used to derive landscape metrics. We found that Amur Falcons chose a wide range of nesting sites, but significantly preferred nests with a domed roof. Breeding pairs of Eurasian Hobby Falco subbuteo and Eurasian Magpie were often found to breed near the nest in about the same distance as neighboring Amur Falcon pairs. Additionally, the occurrence of the species was positively associated with bare soil cover, forest cover, and shrub patches within their home range and negatively with the distance to wetlands. Areas of wetlands and fallow land might be used for foraging since Amur Falcons mostly depend on an insect diet. Additionally, we found that rarely burned habitats were preferred. Overall, the effect of landscape variables on the choice of actual nest sites appeared to be rather small. We used different classification methods to predict the probability of occurrence, of which the Random forest method showed the highest accuracy. The areas determined as suitable habitat showed a high concordance with the actual nest locations. We conclude that Amur Falcons prefer to occupy newly built (domed) nests to ensure high nest quality, as well as nests surrounded by available feeding habitats.     

An ‘ecological trap’ for yellow warbler nest microhabitat selection

Contrary to assumptions of habitat selection theory, field studies frequently detect ‘ecological traps’, where animals prefer habitats conferring lower fitness than available alternatives. Evidence for traps includes cases where birds prefer breeding habitats associated with relatively high nest predation rates despite the importance of nest survival to avian fitness. Because birds select breeding habitat at multiple spatial scales, the processes underlying traps for birds are likely scale‐dependent. We studied a potential ecological trap for a population of yellow warblers Dendroica petechia while paying specific attention to spatial scale. We quantified nest microhabitat preference by comparing nest‐ versus random‐site microhabitat structure and related preferred microhabitat features with nest survival. Over a nine‐year study period and three study sites, we found a consistently negative relationship between preferred microhabitat patches and nest survival rates. Data from experimental nests described a similar relationship, corroborating the apparent positive relationship between preferred microhabitat and nest predation. As do other songbirds, yellow warblers select breeding habitat in at least two steps at two spatial scales; (1) they select territories at a coarser spatial scale and (2) nest microhabitats at a finer scale from within individual territories. By comparing nest versus random sites within territories, we showed that maladaptive nest microhabitat preferences arose during within‐territory nest site selection (step 2). Furthermore, nest predation rates varied at a fine enough scale to provide individual yellow warblers with lower‐predation alternatives to preferred microhabitats. Given these results, tradeoffs between nest survival and other fitness components are unlikely since fitness components other than nest survival are probably more relevant to territory‐scale habitat selection. Instead, exchanges of individuals among populations facing different predation regimes, the recent proliferation of the parasitic brown‐headed cowbird Molothrus ater, and/or anthropogenic changes to riparian vegetation structure are more likely explanations.     

NOTES ON SOME MARSH BIRDS OF CAPE SAN ANTONIO,ARGENTINA*

During an 11-month study of the Black-headed Duck in eastern Argentina, observations were made on the marsh birds of Cape San Antonio, Province of Buenos Aires. These observations supplement the distributional and life history obtained by Gibson (1879–1920), Wetmore (1926) and others. The deep, fresh-water marshes characteristically are dominated by one of three plants: tules, cutgrass or cat-tails. There were surprisingly few marshes with mixtures of these plants and few marshes which showed a gradual transition from marsh to uplands. Marsh birds showed considerable adaptation in chronology of nesting and nest-site selection for the seasonal water cycle of wet springs and dry periods in the late summer and fall. Some marsh birds were involved in nesting over a longer period than is usual in Northern Hemisphere marshes. As seems characteristic of all marsh birds, cover-water edges were usual sites for nests. There were only a few species with restricted nest-site selection, and competition between closely related species was noted only among the three species of coots. A list of the marsh birds of the area is given, and comments are presented on the ecology and behaviour of selected species.     

Changing patterns of nest predation and predator communities along a tropical elevation gradient

Tropical montane communities host the world's highest beta diversity of birds, a phenomenon usually attributed to community turnover caused by changes in biotic and abiotic factors along elevation gradients. Yet, empirical data on most biotic factors are lacking. Nest predation is thought to be especially important because it appears to be common and can change selective pressures underlying life history traits, which can alter competitive interactions. We monitored 2538 nests, 338 of which had known nest predators, to evaluate if nest predation changes along a tropical elevational gradient. We found that nest predation decreased with elevation, reflecting the loss of lowland predators that do not tolerate colder climates. We found different “super” nest predators at each elevation that accounted for a high percentage of events, suggesting that selection pressures exerted by nest predator communities may be less diffuse than has been hypothesized, at least for birds nesting in the understory.     

Modeling Habitat Change in Salt Marshes After Tidal Restoration

Salt marshes continue to degrade in the United States due to indirect human impacts arising from tidal restrictions. Roads or berms with inadequate provision for tidal flow hinder ecosystem functions and interfere with self‐maintenance of habitat, because interactions among vegetation, soil, and hydrology within tidally restricted marshes prevent them from responding to sea level rise. Prediction of the tidal range that is expected after restoration relative to the current geomorphology is crucial for successful restoration of salt marsh habitat. Both insufficient (due to restriction) and excessive (due to subsidence and sea level rise) tidal flooding can lead to loss of salt marshes. We developed and applied the Marsh Response to Hydrological Modifications model as a predictive tool to forecast the success of management scenarios for restoring full tides to previously restricted areas. We present an overview of a computer simulation tool that evaluates potential culvert installations with output of expected tidal ranges, water discharges, and flood potentials. For three New England tidal marshes we show species distributions of plants for tidally restricted and nonrestricted areas. Elevation ranges of species are used for short‐term (<5 years) predictions of changes to salt marsh habitat after tidal restoration. In addition, elevation changes of the marsh substrate measured at these sites are extrapolated to predict long‐term (>5 years) changes in marsh geomorphology under restored tidal regimes. The resultant tidal regime should be designed to provide habitat requirements for salt marsh plants. At sites with substantial elevation losses a balance must be struck that stimulates elevation increases by improving sediment fluxes into marshes while establishing flooding regimes appropriate to sustain the desired plants.     

Climate change and loss of saltmarshes: consequences for birds

Saltmarshes are areas of vegetation subject to tidal inundation and are important to birds for several reasons. Saltmarshes are areas of high primary productivity and their greatest significance for coastal birds is probably as the base of estuarine food webs, because saltmarshes export considerable amounts of organic carbon to adjacent habitats, particularly to the invertebrates of mudflats. In addition, saltmarshes are of direct importance to birds by providing sites for feeding, nesting and roosting. Climate change can affect saltmarshes in a number of ways, including through sea-level rise. When sea-level rises the marsh vegetation moves upward and inland but sea walls that prevent this are said to lead to coastal squeeze and loss of marsh area. However, evidence from southeast England, and elsewhere, indicates that sea-level rise does not necessarily lead to loss of marsh area because marshes accrete vertically and maintain their elevation with respect to sea-level where the supply of sediment is sufficient. Organogenic marshes and those in areas where sediment may be more limiting (e.g. some west coast areas) may be more susceptible to coastal squeeze, as may other marshes, if some extreme predictions of accelerated rates of sea-level rise are realized.     

Nest‐site selection by Slender‐billed Parakeets in a Chilean agricultural‐forest mosaic

ABSTRACT Species in the family Psittacidae may be particularly vulnerable to anthropogenic habitat transformations that reduce availability of suitable breeding sites at different spatial scales. In southern Chile, loss of native forest cover due to agricultural conversion may impact populations of Slender‐billed Parakeets (Enicognathus leptorhynchus), endemic secondary cavity‐nesting psittacids. Our objective was to assess nest‐site selection by Slender‐billed Parakeets in an agricultural‐forest mosaic of southern Chile at two spatial scales: nest trees and the habitat surrounding those trees. During the 2008–2009 breeding seasons, we identified nest sites (N= 31) by observing parakeet behavior and using information provided by local residents. Most (29/31) nests were in mature Nothofagus obliqua trees. By comparing trees used for nesting with randomly selected, unused trees, we found that the probability of a tree being selected as a nest site was positively related to the number of cavity entrances, less dead crown, and more basal injuries (e.g., fire scars). At the nesting‐habitat scale, nest site selection was positively associated with the extent of basal injuries and number of cavity entrances in trees within 50 m of nest trees. These variables are likely important because they allow nesting parakeets to minimize cavity search times in potential nesting areas, thereby reducing energetic demands and potential exposure to predators. Slender‐billed Parakeets may thus use a hierarchical process to select nest sites; after a habitat patch is chosen, parakeets may then inspect individual trees in search of a suitable nest site. Effective strategies to ensure persistence of Slender‐billed Parakeets in agricultural‐forest mosaics should include preservation of both individual and groups of scattered mature trees.     

Nesting habitat and nest features of Water Rails Rallus aquaticus and Little Crakes Zapornia parva on large wetlands

ABSTRACT

Capsule: In large and medium wetlands with extended reed beds Phragmites and cattail Typha dominated areas, Water Rails Rallus aquaticus and Little Crakes Zapornia parva show higher differences in nesting sites in contrast with other populations from small and fragmented wetlands, where the ranges of values for environmental variables at nesting sites overlap greatly.

Aims: To investigate the nesting sites and nesting habitats of both species to a fine scale, on medium and large wetlands, to evaluate the potential overlapping of nesting habitat and to compare data with those obtained in small wetlands.

Methods: In the study area, the Fize? Basin, Romania, 17 wetlands, ponds and reed beds ranging from 11.78 to 252.68 ha were investigated. The species were present on 4 wetlands, which were subsequently surveyed for nests. Between April and August 2010–2012, a total of 83 Water Rail and 46 Little Crake nests were found, measured and analysed in terms of nesting habitat and nest features.

Results: Principal component analyses suggest no overlap in nest site selection and a partial overlap in the nest features. An analysis of similarity confirmed significant nest structural differences. A discriminant function analysis highlights the main factors dividing the nest features of both species being: water depth and distance between the nest and a water surface. Little Crakes build their nests in cattail Typha sloped clumps, while Water Rails build their nests near reed Phragmites strains.

Conclusion: In large and medium wetlands, Water Rails nest deep in the reed bed rather than in other types of habitats, contrary to what has been reported for small ponds areas. Little Crakes nest in cattail independently of the size of the wetland where they occur.     

A Ground-Nesting Galliform’s Response to Thermal Heterogeneity: Implications for Ground-Dwelling Birds

The habitat selection choices that individuals make in response to thermal environments influence both survival and reproduction. Importantly, the way that organisms behaviorally respond to thermal environments depends on the availability and juxtaposition of sites affording tolerable or preferred microclimates. Although, ground nesting birds are especially susceptible to heat extremes across many reproductive stages (i.e., breeding, nesting, brood rearing), the mechanistic drivers of nest site selection for these species are not well established from a thermal perspective. Our goal was to assess nest site selection relative to the configuration of the thermal landscape by quantifying thermal environments available to a ground-nesting bird species inhabiting a climatically stressful environment. Using northern bobwhite (Colinus virginanus) as a model species, we measured black bulb temperature (T_bb) and vegetation parameters at 87 nests, 87 paired sites and 205 random landscape sites in Western Oklahoma during spring and summer 2013 and 2014. We found that thermal space within the study area exhibited differences in T_bb of up to 40°C during peak diurnal heating, resulting in a diverse thermal landscape available to ground-nesting birds. Within this thermally heterogeneous landscape, nest sites moderated T_bb by more than 12°C compared to random landscape sites. Furthermore, successful nests remained on average 6°C cooler than unsuccessful nests on days experiencing ambient temperatures ≥ 39°C. Models of future T_bb associated with 2080 climate change projections indicate that nesting bobwhites will face substantially greater T_bb throughout the landscape for longer durations, placing an even greater importance on thermal choices for nest sites in the future. These results highlight the capacity of landscape features to act as moderators of thermal extremes and demonstrate how thermal complexity at organism-specific scales can dictate habitat selection.     

Nesting habitat of Warbling Vireos across an elevational gradient in the southern Sierra Nevada

ABSTRACT.   Populations of Warbling Vireos ( Vireo gilvus ) are declining in California, apparently due to low reproductive success. From 1989–2002, I studied the nest-site selection and reproductive success of Warbling Vireos across an elevational gradient in the southern Sierra Nevada. Warbling Vireos regularly nested in upland coniferous forests with few or no deciduous trees, and tree species used by nesting vireos included five species of conifers and four species of deciduous trees. Overall, hardwoods were used more than expected based on their availability, but 69% of all nests were in conifers. Hardwood trees were found only in low and mid-elevation ponderosa pine ( Pinus ponderosa ) and mixed-conifer sites. In low-elevation ponderosa pine habitat, 87% of nests were in hardwoods, with 67% in California black oaks ( Quercus kelloggii ), a species that typically occupies upland sites. In mixed-conifer sites where reproductive success was high, 65% of nests were in incense cedar ( Calocedrus decurrens ) and California black oak was the next most commonly used species. Because fire suppression has likely increased numbers of shade-tolerant tree species like incense cedar, shade-intolerant species like black oaks may have been more important as a nest substrate for vireos in the past. Only conifers were used as nesting substrates at higher elevations. Nest success was greater for Warbling Vireos that nested in tall trees in areas with high basal area. My results suggest that Warbling Vireos in the Sierra Nevada would benefit from management activities that encourage retention and recruitment of California black oaks at lower elevations, and development of stands with large trees, dense foliage, and semi-open canopy throughout their elevation range.     

Selection indicates preference in diverse habitats: a ground-nesting bird (Charadrius melodus) using reservoir shoreline

Animals use proximate cues to select resources that maximize individual fitness. When animals have a diverse array of available habitats, those selected could give insights into true habitat preferences. Since the construction of the Garrison Dam on the Missouri River in North Dakota, Lake Sakakawea (SAK) has become an important breeding area for federally threatened piping plovers (Charadrius melodus; hereafter plovers). We used conditional logistic regression to examine nest-site selection at fine scales (1, 3, and 10 m) during summers 2006-2009 by comparing characteristics at 351 nests to those of 668 random sites within nesting territories. Plovers selected sites (1 m(2)) that were lower than unused random sites, increasing the risk of nest inundation. Plovers selected nest sites that were flat, had little silt, and at least 1 cobble; they also selected for 3-m radius nest areas that were relatively flat and devoid of vegetation and litter. Ninety percent of nests had <38% coverage of silt and <10% slope at the site, and <15% coverage of vegetation or litter and <31% slope within the 3-m radius. Gravel was selected for at nest sites (11% median), but against in the area 10-m from the nest, suggesting plovers select for patches or strips of gravel. Although elevation is rarely evaluated in studies of ground-nesting birds, our results underscore its importance in habitat-selection studies. Relative to where plovers historically nested, habitat at SAK has more diverse topography, substrate composition, vegetation communities, and greater water-level fluctuations. Accordingly, our results provide an example of how habitat-selection results can be interpreted as habitat preferences because they are not influenced by desired habitats being scarce or absent. Further, our results will be useful for directing habitat conservation for plovers and interpreting other habitat-selection studies.     

American Black Duck Nesting Ecology in North Carolina

North Carolina, USA, is the southernmost extent of the American black duck's (Anas rubripes) breeding range; however, little is known about their nesting ecology in this region. We located and monitored 140 nesting black ducks over 2 years (2017–2018) to quantify preferred nesting habitat and assess nesting productivity within coastal North Carolina. We located nests in brackish marshes (75%) and man-made dredge spoil islands (25%) at a density of 1 nest/22 ha. Black ducks selected high marsh and nested an average of 21.81 m from open water at a mean elevation of 1.36 m. In preferred nesting habitat, visual obstruction readings were 0.50 m with a maximum mean vegetation height of 0.81 m and land cover consisted largely of grasses (84.6%). Apparent nest success rates varied from 31% (2017) to 63% (2018) across years. The majority (72.2%) of variability in nest success was best predicted by nest location (mainland marsh, natural island, or spoil island), vegetation density, maximum vegetation height, and year. Management for breeding black ducks in coastal North Carolina should focus on promoting selected nesting habitat and reducing nest predators. Prescribed burns, used to set back succession on spoil islands and in brackish marshes should be conducted in the winter or in the early growing season not to exceed the twenty-fifth quantile date of black duck nest initiation (2 Apr). © 2021 The Wildlife Society.     

Use of mistletoes by the Grey Go‐away‐bird (Corythaixoides concolor,Musophagidae) in a semi‐arid savannah,south‐west Zimbabwe

Mistletoes are preferred nesting sites for many bird species in a range of habitats. However, no studies have examined the use of mistletoes by nesting birds in the semi‐arid savannah. We studied nesting in mistletoe and its role in determining nesting success in the Grey Go‐away‐bird in south‐west Zimbabwe. We modelled the effects of mistletoe, mistletoe abundance, nest microclimate, concealment and nest height on daily survival rates (DSR) using program MARK. A constant survival model was best fitted for the Grey Go‐away‐bird suggesting a constant nest survival rate across the nesting period. Mistletoe nests had lower DSR than nests placed elsewhere in the canopy. Mistletoe abundance and nest height had a positive association with DSR whereas visibility distance, microclimate and concealment were negatively associated with DSR. Overall, survival for nests in mistletoe was 22.1% compared with 90.5% for nests in other substrates over the 50‐day nesting period. In conclusion, the low nest survival in mistletoe suggests either that the factors used to select mistletoe as nest sites by these birds are poor predictors of nest success or that nesting in mistletoe may be maladaptive.     

Altitudinal variation in sexual dimorphism: a new pattern and alternative hypotheses

The colder climate and disjunct distribution of nesting andforaging habitats at high elevations increases the necessityof biparental care for successful breeding in birds. If differencesin parental investment between the sexes correlate with intensityof sexual selection, the intensity of sexual selection shouldcovary with ecological factors associated with elevation. Iused sexual dimorphism as an indirect measure of intensity ofsexual selection and examined variation in sexual dimorphismin 126 extant species of cardueline finches. I controlled forphylogeny and potential confounding factors and tested the predictionthat the extent of sexual dimorphism negatively covaries withelevation of breeding. As predicted, interspecific variationin sexual dimorphism was more strongly associated with changesin elevation than with habitat, nest dispersion and placement,and migratory status. Species occupying lower elevations weremore sexually dimorphic in plumage than species at higher elevations.This variation was largely due to increased brightness of maleplumage at lower elevations. I address possible explanationsof this trend, which may include increased opportunities forextrapair fertilizations at lower elevations, an increase inthe cost of secondary sexual trait production (i.e., molt) andmaintenance at high elevations, and elevational variation inpredation pressure     

Nesting habitat characteristics of Marbled Murrelets occurring in near‐shore waters of the Olympic Peninsula,Washington

Marbled Murrelets (Brachyramphus marmoratus) are listed as threatened in the portion of their range extending from British Columbia to California due to loss of nesting habitat. Recovery of Marbled Murrelet populations requires a better understanding of the characteristics of their nesting habitat in this part of their range. Our objective, therefore, was to describe their nesting habitat in Washington State and Vancouver Island, British Columbia. We captured Marbled Murrelets from 2004 to 2008, fitted them with radio transmitters, and followed them to nests (N = 20). We used Cohen's unbiased d effect size to assess differences between forest plots surrounding nest sites and nearby control sites (N = 18). Nest sites had less canopy cover of the dominant conifers and fewer, but larger, trees than control sites. Nest sites also had greater percentages of trees with platforms >10 cm diameter and >15 cm diameter, and more platforms of these sizes than control sites. The mean diameter at breast height of nest trees was 136.5 cm (range = 84–248 cm) and all but one nest was in dominant or co‐dominant tree species. At the landscape scale, we used vegetation maps derived from remotely sensed data and found greater canopy cover, higher density of mature trees, more platforms >10 cm/ha, and more old‐growth habitat at nest sites than at random sites. Our findings suggest that, at the site scale, nesting Marbled Murrelets selected the most suitable features of forest structure across expansive potentially suitable habitat. Our landscape‐scale analysis showed that habitat features in nesting stands differed from those features in available stands in the murrelet's range in Washington. We also found that stands with nests were less fragmented than available forest across murrelet range. All nest sites of radio‐tagged birds in Washington were in protected areas in mostly undisturbed forest habitat. Conservation of these areas of inland nesting habitat will be critical to the recovery of Marbled Murrelet populations.     

Avian predators in a meadow landscape: consequences of their occurrence for breeding open‐area birds

We examined the occurrence of six species of meadow birds (four wader species and two songbird species) in relation to the distance to the nest location of an avian predator (three species). We related our findings to the degree of openness of the landscape in which this avian predator nest was located. The degree of openness varied from very open to very closed, depending on the number of view‐obstructing landscape elements in the landscape (none or very few in open ones, but completely covered with forest or built‐up area in very closed landscapes). We used a dataset containing nesting locations of meadow birds and predators in the province of Gelderland, the Netherlands, allowing us to perform the analysis on three grid cell sizes (100×100 m, 250×250 m and 500×500 m). Our results show that, for each grid cell size, all meadow bird species showed highest nesting densities in open landscapes. Lowered densities were found around occupied nests of avian predators, irrespective whether the predator's nest was situated in an open or closed landscape. The preference of meadow birds for open landscapes away from predator's nests suggests that a large visibility, that allows them to scan for predators to be able to chase them away in time, is an important habitat requirement for meadow birds to select a nest site. It also suggests that openness of the landscape, independent from the presence of occupied predator's nests, is a factor in selecting a nest site. In contrast, for two out of three species of avian predator, we found that they chose more closed landscapes to nest because these species nest in landscape elements like wood lots and lone trees which make the landscape more closed by definition. For the third avian predator species, the grid cell size was probably too small to find a consistent result, as that species has territories larger than even the largest grid cell size we used.