Habitat associations and breeding success of the Chaffinch Fringilla coelebs

Capsule Population trends for Chaffinch on farmland are unlikely to be explained by their preference for non-crop habitats alone.

Aims To investigate the importance of non-cropped habitats for Chaffinch territory distribution, breeding success and foraging habitat selection in Scottish farmland.

Methods Territory distribution, nesting success and foraging behaviour of adults feeding chicks at the nest were recorded and related to habitat composition on two Scottish lowland farms.

Results Higher Chaffinch territory densities were associated with the presence of hedgerows, trees and grass leys, whereas lower densities were found adjacent to winter Barley. Nests were predominantly located in conifer trees and hedgerows. Trees were selected preferentially for foraging. Poor breeding success was detected in nests associated with cereal crops and wider field margins. Farmland in Scotland supported much lower territory densities than in England.

Conclusion Chaffinches rely predominantly on non-cropped habitats for territory establishment, nesting and foraging habitats. Differences in habitat composition between England and Scotland may explain differences in territory densities. However, the Chaffinch's preference for non-crop habitats is unlikely to explain its population trends alone. Immigration from other habitats and/or a decrease in inter-specific competition for resources may also have contributed to the increase in the national farmland Chaffinch population.     

Multi-scale habitat selection and foraging ecology of the eurasian hoopoe (<Emphasis Type="Italic">Upupa epops</Emphasis>) in pine plantations

Bird conservation can be challenging in landscapes with high habitat turnover such as planted forests, especially for species that require large home ranges and juxtaposition of different habitats to complete their life cycle. The eurasian hoopoe (Upupa epops) has declined severely in western Europe but is still abundant in south-western France. We studied habitat selection of hoopoes in pine plantation forests using a multi-scale survey, including point-counts at the landscape level and radio-tracking at the home-range scale. We quantified habitat use by systematically observing bird behaviour and characterized foraging sites according to micro-habitat variables and abundance of the main prey in the study area, the pine processionary moth (Thaumetopoea pityocampa). At the landscape scale, hoopoes selected habitat mosaics of high diversity, including deciduous woods and hedgerows as main nesting sites. At the home-range scale, hoopoes showed strong selection for short grassland vegetation along sand tracks as main foraging habitats. Vegetation was significantly shorter and sparser at foraging sites than random, and foraging intensity appeared to be significantly correlated with moth winter nest abundance. Hoopoe nesting success decreased during the three study years in line with processionary moth abundance. Thus, we suggest that hoopoes need complementation between foraging and breeding habitats to establish successfully in pine plantations. Hoopoe conservation requires the maintenance of adjacent breeding (deciduous woods) and foraging habitats (short swards adjacent to plantation edges), and consequently depends on the maintenance of habitat diversity at the landscape scale.     

Foraging in space and time structure an African small mammal community

We used live-trapping and foraging to test for the effect of habitat selection and diet on structuring a community of six small mammals and one bird within the Soutpansberg, South Africa. We established grids that straddled adjacent habitats: woodland, rocky hillside, and grassland. Trapping and foraging were used to estimate abundance, habitat use, and species-specific foraging costs. The species with the highest abundance and foraging activity in a habitat, activity time, or food was considered the most efficient and presumed to have a competitive advantage. All species exhibited distinct patterns of spatial and temporal habitat preference which provided the main mechanism of coexistence, followed by diet selection. The study species were organized into three assemblages (α diversity): grassland, Rhabdomys pumilio, Dendromus melanotis, and Mus minutoides.; woodland, Aethomys ineptus and Micaelamys namaquensis; and rock-dwelling, M. namaquensis and Elephantulus myurus. Francolinus natalensis foraged in open rocky areas and under wooded islands within the grassland. Species organization across the habitats suggested that feeding opportunities are available within all habitats; however, distinct habitat preferences resulted from differing foraging aptitudes and efficiencies of the competing species. At Lajuma, species distribution and coexistence are promoted through distinct habitat preferences that were shaped by competition and species-specific foraging costs. The combination of trapping and foraging provided a mechanistic approach that integrates behavior into community ecology by ‘asking’ the animal to reveal its perspective of the environment. Using spatial and temporal foraging decisions—as behavioral indicators—enables us to guide our understanding for across-taxa species coexistence.     

Multi-scale habitat selection affects offspring survival in a precocial species

In theory, habitat preferences should be adaptive. Accordingly, fitness is often assumed to be greater in preferred habitats; however, this assumption is rarely tested and, when it is, the results are often equivocal. Habitat preferences may not directly convey fitness advantages if animals are constrained by tradeoffs with other selective pressures like predation or food availability. We address unresolved questions about the survival consequences of habitat choices made during brood-rearing in a precocial species with exclusive maternal care (mallard Anas platyrhynchos, n = 582 radio-marked females on 27 sites over 8 years). We directly linked duckling survival with habitat selection patterns at two spatial scales using logistic regression and model selection techniques. At the landscape scale (55–80 km²), females that demonstrated stronger selection of areas with more cover type 4 wetlands and greater total cover type 3 wetland area (wetlands with large expanses of open water surrounded by either a narrow or wide peripheral band of vegetation, respectively) had lower duckling survival rates than did females that demonstrated weaker selection of these habitats. At finer scales (0.32–7.16 km²), females selected brood-rearing areas with a greater proportion of wetland habitat with no consequences for duckling survival. However, females that avoided woody perennial habitats composed of trees and shrubs fledged more ducklings. The relationship between habitat selection and survival depended on both spatial scale and habitats considered. Females did not consistently select brood-rearing habitats that conferred the greatest benefits, an unexpected finding, although one that has also been reported in other recent studies of breeding birds.     

Habitat associations of Eurasian Skylarks Alauda arvensis breeding on Irish farmland and implications for agri-environment planning

Capsule Skylarks breeding in Ireland prefer extensive grassland habitats and almost completely avoid tillage habitats.

Aims To describe the distribution and habitat use of breeding Skylarks in Ireland, particularly in lowland agricultural habitats, and to use this information to inform conservation measures for this species.

Methods Countryside Bird Survey (CBS) and Farmland Bird Project (FBP) data were examined to determine large-scale (national) distribution and habitat selection, in addition to smaller-scale (farm- and field-level) habitat use. The CBS is a national breeding bird monitoring scheme involving 397 1-km squares. The FBP collected detailed bird and habitat data from 122 farms.

Results CBS and FBP data both showed significant regional differences in breeding Skylark densities, with the highest relative abundances in the northwest and west. Dry grassland/grass moor habitats supported the highest densities of breeding Skylarks in the CBS, which were significantly higher than in improved grassland or tillage. At the farm-level, Skylark numbers were positively related to wetland habitats but negatively associated with trees in field boundaries, dense ground vegetation and overall density of farm boundaries. At the field-scale, larger fields and unimproved grasslands were preferred.

Conclusion Agri-environment measures tailored to region-specific requirements and to the relatively local habitat preferences of target species are required if population declines of species of conservation concern, including Skylarks, are to be reversed.     

Between land abandonment and agricultural intensification: habitat preferences of Red-backed Shrikes Lanius collurio in low-intensity farming conditions

Capsule The conservation of Red-backed Shrikes on farmland habitats depends on extensive farming conditions.

Aims To evaluate breeding density and habitat preferences of the declining Red-backed Shrike and relate its occurrence to an environmental gradient ranging from land abandonment to intensive farming.

Methods The study was carried out in the Apennines (northern Italy), at nine 21-ha study plots. We identified factors affecting breeding density and habitat preferences at two spatial scales (landscape and territory) and analysed the variation in territory density according to the relative farming intensity in a low-intensity agricultural landscape.

Results The presence of shrubs and cultivated/grazed land positively influenced the number of Red-backed Shrike territories per plot, while the species' settlement within plots was related to higher values of shrub cover and the presence of hedges. Shrike occurrence was associated with land-use categories intermediate between land abandonment and intensive agriculture.

Conclusions This study provides a first detailed assessment of Red-backed Shrike habitat requirements in southern Europe. Favoured habitats were pasture/cultivation mosaics flanked by or interspersed with shrubs/hedges (15–20% of the surface of the 1-ha medium-sized territory). Thus, the conservation of Red-backed Shrikes in low-intensity southern European farmland appears to reflect a trade-off between agricultural intensification and long-term land abandonment.     

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.     

Adaptive habitat preferences in the Tawny Owl Strix aluco

Capsule: Tawny Owls Strix aluco occupying nest boxes preferred habitats which were positively associated with the probability of nesting success.

Aims: We aimed to determine whether or not: (1) Tawny Owls showed habitat preferences when occupying nest boxes; (2) nesting performance was related to the habitats around occupied nest boxes and (3) habitat availability had changed around available and occupied nest boxes between 1995–2004 and 2005–14.

Methods: Tawny Owls were studied using nest boxes erected in a commercial forest. During nest boxes checks (724 cases), data on occupancy and nesting performance (88 cases) were recorded, and habitat within a 0.4?km radius around nest boxes was analysed.

Results: Tawny Owls had preferences for clearings within forests, mature forests and grasslands but avoided young forests. We found a positive relationship between nesting success and abundance of clearings within the forest, and a negative relationship between nesting success and abundance of young forests. A change in habitat preferences over the two decades was evident, but habitat availabilities remained similar.

Conclusions: Findings indicate adaptive habitat selection in Tawny Owls because preferred habitats were associated with higher fitness and this type of habitat became more frequently selected over time.     

Do trappers understand marten habitat?

Previous studies of the effects of fur trapping on marten populations have not considered habitat variation and how trappers use available habitat. We investigated the behavior of fur trappers with respect to roads, waterways, and the forest habitats on trap lines, using registered trap lines in northern Ontario as a study system. The objectives of this study were to 1) develop models for predicting trap location based on access and habitat features, 2) determine whether trappers target the same habitat preferred by American marten, and 3) investigate effects of spatial resolution on predictive models, using a geographic information system (GIS) for coarse resolution variables and direct forest mensuration for fine resolution variables. Distance to roads and water were by far the most influential factors in logistic models for predicting trap presence, accounting for 51.2–61.7% of the observed deviance. At a coarse spatial resolution, trappers selected sites that were close to vehicular access, and in older mixed wood forest stands. Similarly, at a coarse resolution, marten selected old stands, but dominated by coniferous trees. At a finer spatial resolution, trappers selected sites with high basal area of trees, pronounced proportion of black spruce, high canopy cover, and high density of coarse woody debris, consistent with previous studies on marten habitat selection at a fine resolution. Although coarse resolution models are easily applicable because of the wide availability of GIS land cover data, fine resolution models had greater predictive power when considering habitat variables. By quantifying trapper behaviors, these results suggest that the effectiveness of marten sanctuaries used in forest management depend not only on the age and species composition of forest stands left unlogged, but also on the degree to which they are accessible to trappers. © 2012 The Wildlife Society.     

Breeding ecology and habitat selection of Merlin Falco columbarius in forested landscapes

Capsule: Long-term trends in Merlin Falco columbarius breeding performance remained stable during a period of extensive afforestation in Ireland, where Merlin predominantly select conifer plantations for nesting.

Aims: To determine breeding performance and habitat selection of Merlin in a landscape significantly altered by afforestation.

Methods: We compiled data on Merlin to determine long-term trends in breeding performance and to examine habitat selection in a country with one of the fastest rates of afforestation in Europe.

Results: Merlin predominantly nested in trees (99.5%; n?=?183 pairs), with a strong preference for conifer plantations, which accounted for over 12 times more nests than expected by random selection. Moors and heathland were strongly selected as land-uses adjacent to nest sites. Most nests were located within 10?m of the forest edge, and in forests aged between 31 and 40 years. Merlin showed positive selection for moors and heathland, peat bogs and natural grasslands within breeding territories, and breeding success was positively related to the proportion of these land-uses surrounding nests. Breeding was successful for 74% of nests (n?=?300), and mean productivity was 2.1 young per breeding attempt (n?=?265) between 1982 and 2014. Breeding parameters remained constant over the 33-year study period, despite an increase of more than 75% in forest cover during this time.

Conclusion: Merlin breeding performance showed no long-term effects of increased afforestation. Although Merlin predominantly nested in conifer plantations, the presence of nearby open suitable foraging habitats influenced nest site selection and breeding success. The nesting preference of Merlin makes them vulnerable to disturbance from forest operations, which requires mitigation.     

Habitat selection and foraging success of Hen Harriers Circus cyaneus in west Scotland

The foraging behaviour of Hen Harriers breeding in west Scotland was studied in a variety of afforested and moorland habitats. Time budget information from sample areas, stratified by habitat type and controlled for nest distance, was used to investigate habitat selection. Preferences were then related to measures of foraging performance in each habitat. Hen Harriers foraged preferentially over young first rotation coniferous forests, and selected heathland and grassland habitats ahead of closed canopy woodland. Harrier preference for the various habitats was positively correlated with the frequency with which they struck at, and captured, prey. Prey strike success was much lower than that reported for moorland managed for Red Grouse Lagopus lagopus scoticus. The results explain many of the reported changes in local Hen Harrier populations. The extent of young first rotation forestry is currently in decline. It is predicted that this will lead to a reduction in numbers of Hen Harriers breeding in west Scotland, and an increase in the proportion of the British harrier population occupying moorland managed for Red Grouse.     

Vegetation structure influences foraging decisions in a declining grassland bird: the importance of fine-scale habitat and grazing regime

Capsule: Whinchat Saxicola rubetra foraging behaviour was significantly influenced by habitat structure and grazing.

Aims: To assess how foraging habitats selected by breeding Whinchats differed from wider territory attributes under contrasting grazing management in multiple upland areas in Scotland: principally sheep grazed, Red Deer grazed or ungrazed, and to identify how differing land use may limit suitable foraging areas.

Methods: We compared fine-scale vegetation structure in patches chosen for foraging by Whinchats in contrasting grazing management regimes.

Results: Whinchats were less likely to forage in patches with a greater cover of bracken and tall non-bracken vegetation, regardless of grazing regime. Grass cover influenced foraging behaviour in ungrazed habitats only, where Whinchats were less likely to forage in areas with high grass cover.

Conclusion: Whinchats appear to require a mosaic or range of sward structures within breeding territories, highlighting the importance of establishing how vegetation structure influences breeding birds at different spatial scales. Our results suggest that suitable foraging patches were plentiful within grazed habitats but potentially limited in ungrazed habitats. Further work is needed to identify management regimes and interventions to maintain conditions suitable for breeding Whinchats that are compatible with other land use and conservation objectives.     

Habitat selection by nocturnal passerine migrants en route: mechanisms and results

Habitat use and habitat selection are essential for successful stopovers. Passerine migrants use habitats in a clearly non-random manner, even if many species utilise a broader range of habitats during passage than during breeding or wintering. Habitat selection proceeds as a sequence of events: landfall; search/settling, including redistribution across habitats if necessary; and habitat exploitation, with all stages probably condition-dependent. This review is aimed at studying this sequence and also the factors which govern decision-making in nocturnal passerine migrants at all levels. In most cases, habitats are (pre)selected by migrants already at landfall using both visual and acoustic cues. After landfall, migrants start to perform direct sampling of habitats during which they may move constantly and perform fine-tuning of their habitat choice. Some species subsequently occupy a small home range in a particular (micro)habitats, whereas others continue to move broadly during the whole stopover period. An interaction of several factors shapes the use of habitats after landing, among which are migrants’ innate preferences and functional morphology, foraging strategies and food resource distribution, habitat carrying capacity and exposure to predators. The large-scale spatial context probably also plays a role which might be currently underestimated.     

Use of field margins managed under an agri-environment scheme by foraging Barn Swallows Hirundo rustica

Capsule: Barn Swallows Hirundo rustica were more likely to forage along arable field margins that were enhanced with wildflowers or legumes than control grass margins.

Aims: To determine if foraging Barn Swallows displayed preferences for specific arable field boundary habitats (grass margins versus floristically enhanced margins) that were managed as part of an agri-environment scheme. We also aim to determine how Barn Swallow food abundance related to these habitats.

Methods: Two foraging activity surveys took place on all grass and floristically enhanced margins (n?=?56) present within the 600 m foraging range of seven Barn Swallow colonies during June and July 2016. Margin habitat use was measured by recording the presence/absence of foraging individuals during surveys, the total number of individuals and by calculating an index of foraging activity. Habitat information relating to adjacent boundary type, transect crop type and neighbouring crop type were also recorded.

Results: Foraging Barn Swallows were significantly more likely to be recorded when survey transects included a floristically enhanced margin, but there was no significant impact of floristically enhanced margins on the total number of individuals recorded or on the index of foraging activity. Foraging activity was higher along grass verges and hedgerows when compared to treelines and was positively related to length weighted Diptera abundance (a measure of food biomass).

Conclusion: Our results suggest that there may be a role for floristically enhanced margins in the conservation of Barn Swallows on arable farmland. More research, however, is needed to determine whether invertebrate-rich agri-environment scheme habitats can influence colony size or improve the breeding success of this species.     

The Origin of Winter Visitors to the British Isles 7. Fieldfare (Turdus pilaris)

Capsule Large‐scale intensification of agricultural management during the past 50 years has resulted in a reduction of invertebrate abundance and higher and denser ground vegetation. Food availability for insectivorous birds foraging on the ground has been negatively affected, but the interactions between birds and their food availability are complex and often species‐specific. Populations of Wrynecks Jynx torquilla are declining all over Europe, possibly because of reduced accessibility to their main prey, ground‐dwelling ants, due to higher and denser ground vegetation. However, it is not clear which ground vegetation structures are tolerated by foraging Wrynecks and which habitats are preferred.

Aims To identify the optimal ground vegetation structure and the main habitat types in which Wrynecks search for food.

Method We radiotracked seven Wrynecks in high‐intensity farmland in Switzerland to study foraging habitat use during the reproduction season. Several habitat variables were mapped at each foraging location and compared with locations selected randomly within individual home ranges.

Results Wrynecks preferentially foraged at places with ≥50% bare ground. Vegetation height was not important. Older fruit tree plantations and fallow land were the preferred foraging habitats.

Conclusion Conservation measures should concentrate on preserving semi‐open agricultural landscape matrices with loose ground vegetation cover to provide suitable foraging conditions. This can be achieved even in intensively managed farmland as illustrated in this study.     

Comparative nest habitat characteristics of sympatric White‐tailed Haliaeetus albicilla and Golden Eagles Aquila chrysaetos in western Scotland

Capsule Golden and White‐tailed Eagles selected different habitats for nesting.

Aim To investigate differences in nesting habitat used by sympatrically breeding eagles in western Scotland, following reintroduction of White‐tailed Eagles from 1975 onwards.

Methods Nest‐site locations from national surveys in 2003–05 were entered into a geographical information system (GIS) in order to measure a set of geographic parameters for each nest site. Binary logistic regression with backwards deletion of non‐significant terms was used to derive minimum adequate models at two spatial scales of the likelihood of an eagle nest belonging to one species or the other. We compared changes in occupancy between 1992 and 2003 of Golden Eagle territories inside and outside a GIS model of potential White‐tailed Eagle habitat and according to proximity to White‐tailed Eagle nests.

Results White‐tailed Eagles nested at lower altitudes than Golden Eagles, in more wooded habitats with more open water close by, tending to nest in trees where these were present. There were 3359 km² of potential White‐tailed Eagle nesting habitat within 25 km of existing White‐tailed Eagle nests, containing 54 Golden Eagle territory centres, but we found no difference in change of occupancy for Golden Eagle territories close to White‐tailed Eagles compared with those further away.

Conclusion White‐tailed and Golden Eagles appear to partition nesting habitat in the west of Scotland by altitude. This corresponds with behaviour in western Norway and with the situation described in historical accounts of nest‐sites in western Scotland prior to extinction of White‐tailed Eagles. It is also consistent with recent studies showing little overlap in breeding season diet of Golden and White‐tailed Eagles in western Scotland, and likely partitioning of foraging habitat by altitude. We conclude that the likelihood of competitive exclusion is less than previously suggested.     

Opportunistic feeding responses of the Yellow-legged Gull Larus michahellis to accessibility of refuse dumps

Capsule The gulls adjust their diet composition and diversity according to refuse dump accessibility.

Aims To examine the influence of the accessibility of open-air refuse dumps on the pre-laying diet of the adult Yellow-legged Gull.

Methods We studied six colonies settled on six rocky islands off the southeastern coast of France. A comparative study of the diet of breeding adults from the six colonies was made through pellet analysis (a total of 848 pellets). We determined the main foraging habitat used (refuse dumps, terrestrial habitats, marine habitat) and the number of foraging habitats used simultaneously (one, two or three), from which we deduced the mean diet diversity.

Results Refuse dumps were consistently the main foraging habitat (evidence in 53–74% of pellets) for the six colonies, even when refuse dump accessibility was low. The majority of pellets contained materials from two simultaneous foraging habitats (evidence in 50–64% of pellets). We demonstrated the influence of a gradient of refuse dump accessibility in terms of adjustment of the pre-laying adult's diet. Indeed, high refuse dump accessibility leads to a poorly diversified diet dominated by refuse. In contrast, when refuse dump accessibility is low, Yellow-legged Gulls broaden their trophic niche, with an increased exploitation of alternative foraging habitats, such as terrestrial habitats.

Conclusion These results show the species' opportunistic feeding and high adaptability, two parameters which need to be known to foresee the consequences on population dynamics, feeding and predatory behaviour of a sudden and severe food shortage, for example due to closure of open-air refuse dumps.     

The Crested Lark Galerida cristata as an example of a bird species that benefits from agricultural management in western Poland

ABSTRACT

Capsule: The Crested Lark Galerida cristata as an example of a species which selects habitats which have undergone agricultural intensification.

Aims: To describe habitat preferences of the Crested Lark in western Poland.

Methods: We surveyed 30 randomly chosen study plots (1?km²) in western Poland to detect breeding pairs of Crested Larks. Sentinel and direct observations in the field were used to provide habitat data. Generalized linear mixed models were used to determine what type of environments habitats were selected by the Crested Larks.

Results: We recorded a total of 106 pairs of Crested Larks in 30 study plots. Birds inhabited farmland environments, where their preferred habitats included buildings, silage, and arable land with cereals.

Conclusion: Silage, which is associated with agricultural intensification within agricultural landscapes, increased the chances of the occurrence of Crested Larks.     

Evidence for density-dependent habitat occupancy at varying scales in an expanding bird population

Understanding factors shaping the spatial distribution of animals is crucial for the conservation and management of wildlife species. However, few studies have investigated density-dependent habitat selection in wild populations in non-equilibrium conditions and at varying spatial scales. Here, we investigated density-dependent habitat selection at varying spatial scales in an increasing white stork Ciconia ciconia population using a long term data set in western France. During a 16-year study period, the breeding population density increased from 0.66 nests per 100 km² to 6.6 nests per 100 km². At the beginning of the colonisation of the area settlement probability of storks was mainly positively affected by grasslands located near wetlands. Areas with intensive or moderately intensive agriculture were extremely unlikely to be occupied by breeding birds. However, selection for the initially preferred habitats faded as stork density increased although the proportions of habitat types remained unchanged. At the same time selection for initially less favoured habitats had increased. Moreover, we found that the spatial scale of selection for each foraging habitat variable was consistent over time. Our results suggest that snapshot analyses of resource selection in populations at high density may be misleading for population conservation or management. In contrast, a longitudinal approach to resource selection can be a valuable tool for understanding resource limitation.