Nest Placement Research Articles

Evidence-based management to regulate the impact of tourism at a key marine turtle rookery on Zakynthos Island, Greece

AbstractThis study evaluates how key beach features influence suitability for nesting by Endangered loggerhead marine turtles Caretta caretta at an internationally important rookery on Zakynthos Island, Greece. During 2007–2009 we assimilated information on beach structure (elevation above sea level and width), the distribution of all nesting (turtle tracks that resulted in nests) and non-nesting (turtle tracks that did not result in nests) turtle emergences from the sea along 6 km of beach, nest placement parameters (distance from sea and elevation above sea level), and beach use by visitors. We found that turtles preferentially emerged on steeper sections of beach, with higher nesting densities occurring on the most environmentally stable beaches. Elevation was a more reliable indicator of nest placement (1 m above sea level) than distance to shore. However, because nests on steeper slopes are located closer to shore, the risk of damage by tourism is increased in such areas. We calculated a potential 36% overlap of natural nest locations with use of the beach by tourists; however, the recorded overlap was 7% because of existing management protocols. This overlap could be further reduced by focusing conservation effort (i.e. further restricting use by people) on beach sections with the steepest inclines. For example, slopes of > 22° comprise 1 km of total beach area annually, the closure of which (above the immediate shoreline to allow passage) would completely protect 50% of nests. This study shows the value of evidence-based management as a practical scientific tool to conserve threatened species in dynamic protected areas that are of both environmental and economic importance.

Nesting and Foraging Characteristics of Aquatic WarblersAcrocephalus paludicolain the Fast Declining Pomeranian Population (NE Germany/ NW Poland)

Limited food availability could be a cause for the strong decline of the small and isolated Aquatic Warbler population in Pomerania (NE Germany/NW Poland). In this paper, we describe nesting site conditions, nest placement and female foraging behaviour as well as food supply in vegetation types prevailing in Pomeranian breeding areas. Female Aquatic Warblers in Pomerania appeared to select ‘managed’ sites (where land use maintains suitable conditions for Aquatic Warbler) for nesting, and preferred vertical structures (ditches and edges within ‘managed’ sites) for foraging. They flew longer distances for provisioning their nestlings than in the core population (E Poland, Belarus) whereas the total distance travelled per 30 minutes was similar. In ‘managed’ sites, the total invertebrate biomass was larger than in ‘unmanaged’ sites in early June when early broods are raised. Pomeranian Aquatic Warblers are able to exploit relatively rich food sources in ‘managed’ meadows and in vertical structures and may thus balance the higher efforts of flights longer than in Eastern Poland and Belarus. To increase the availability of suitable Aquatic Warbler nesting and foraging sites in Pomerania, management by mowing should be continued. It might yield the best results when providing a mosaic of ‘managed’ and ‘unmanaged’ patches.

Nesting patterns of raptors; White backed vulture (<i>Gyps africanus</i>) and African fish eagle (<i>Haliaeetus vocifer</i>), in Lochinvar National Park on the kafue flats, Zambia

This study assessed the nesting patterns of raptors, Gyps africanus and Haliaeetus vocifer in Lochinvar National Park. The main objective of the study was to determine whether tree species, height, girth size, and habitat influenced raptor’s nest placement within Lochinvar National Park. Two species were selected as indicator species for the raptors. Habitat types and tree species were identified and measurements of tree species with nests measured. It was found that the minimum height of nest placement was 10 meters above ground and Acacia woodland was found to be the most preferred habitat for nest placement. Raptors avoided human disturbance by placing their nests at least 100 meters away from human disturbance and from the National park boundary inwards or abandoning if human encroachment comes close to the nest. More research is required to assess nesting materials used, and to determine whether raptors can swap nets or return to the abandoned nests when human disturbance ceases.

白马雪山自然保护区灰头小鼯鼠的巢址特征

PDF HTML阅读 XML下载 导出引用 引用提醒 白马雪山自然保护区灰头小鼯鼠的巢址特征 DOI: 10.5846/stxb201306081474 作者: 作者单位: 西华师范大学西南野生动植物资源保护教育部重点实验室,西华师范大学西南野生动植物资源保护教育部重点实验室,西华师范大学西南野生动植物资源保护教育部重点实验室,西华师范大学西南野生动植物资源保护教育部重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31200294) Nest site characteristics of Petaurista caniceps in Baima Snow Mountain Nature Reserve Author: Affiliation: Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), Institute of Rare Animals and Plants. China West Normal University,,,Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), Institute of Rare Animals and Plants. China West Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:动物的巢为其育幼、避敌和休息等提供了适宜的空间,因此,了解其巢址特征对于物种的保护和管理有着重要的意义。灰头小鼯鼠是一种小型树栖、夜行性哺乳动物,在国内主要分布在中部、南部及西南地区。2012年4月至6月和2012年9月至12月在白马雪山国家级自然保护区对灰头小鼯鼠的巢址特征进行了初步研究。结果表明:灰头小鼯鼠共利用2种巢,在针叶树上,灰头小鼯鼠多利用树枝巢;在阔叶树上,灰头小鼯鼠仅利用树洞巢。巢多紧靠树干(0.2±0.1) m,平均巢高(11.3±0.8) m,巢口无方向偏好。灰头小鼯鼠喜欢选择冠幅更大、通道数更多的树上筑巢,此外,其对郁闭度大,灌木盖度高的生境有明显的选择性。 Abstract:Nests provide a comfortable environment for individuals to raise young, avoid predators and rest, therefore, nesting is a critical facet of life for many species. A detailed understanding of nest site characteristics of species is important for the development of sound conservation and habitat management plan. The Grey-headed flying squirrel (Petaurista caniceps) is a small, nocturnal, arboreal mammal. It is found in southern, central and southwestern China. As a mammal in the list of National Protection of Useful or Have Important Economic and Scientific Research Values in China, little is known about the nest site use of this species. We conducted research on the nest site characteristics of the Grey-headed flying squirrel at three spatial scales (nest placement, nest tree, and nest site) in Baima Snow Mountain National Nature Reserve, Yunnan, China, in order to reveal the important ecological factors affecting the nest site selection of Grey-headed flying squirrel and further enrich wild species ecological and biological data. Data were collected from June to August and September to December 2012. The results showed that Grey-headed flying squirrel preferred two types of nest which included drey and cavity. All nests were found in the live trees. Dreys were typically made up of twigs, bark, moss and other materials. Dreys had larger openings (12.1±0.1) cm (n=15) than those of cavities(10.8±0.5) cm (n=15)(Mann-Whitney U test Z=-3.521, P=0.000), and shallower nests were built in the case of dreys (23.4±1.1) cm than cavities (59.2±1.2) cm (Mann-Whitney U test Z=-4.692, P=0.000). Most nests of the flying squirrel were built close to the main trunk (0.2±0.1) m and at a similar height (11.3±0.8) m (n=30). The average relative height of the nests is (0.67±0.03), indicating that Grey-headed flying squirrel usually built nest in the upper part of the tree. There was significant difference (One-Way ANOVA Test, F1,28=38.865, P=0.000)in the relative height between dreys (0.77±0.03) and cavities (0.51±0.03), but not (One-Way ANOVA Test, F1,28=2.195, P=0.150) in the average nest height. The Grey-headed flying squirrel did not show a significant preference (χ2=13.733,df=7,P=0.056) to the nest entrance direction. We found most cavities in the broadleaf trees (i.e. Quercus aquifolioides, Cyclobalanopsis glauca, Acer oliverianumi) and dreys only in the conifer species (i.e. pinus yunnanensis, Sabina pingii). The DBH (average diameter at breast height) and the average height of drey trees was significantly smaller than those of cavity trees. Characteristics of nest trees and nest sites were compared with randomly selected trees and sites. Grey-headed flying squirrel prefers to the nest trees with larger crown size and more access routes. The results of logistic regression analysis showed that differences in slope, slope position, slope aspect, and distance to water between nest sites and random sites was non-significant. On the contrary, nest sites used by Grey-headed flying squirrel differed from the random sites in that their larger canopy cover and higher shrub cover, suggesting that the Grey-headed flying squirrel seem to select nesting areas with high security and food availability. 参考文献 相似文献 引证文献

Patterns of nest placement of lappet faced vulture (<i>Torgos tracheliotos</i>) in Lochinvar National Park, Kafue Flats, Zambia

This study assessed the nesting patterns oflappet faced vulture inLochinvar National Park, on the Kafue flats,Zambia. Road drives and foot patrols were used to identify and take GPS coordinates of lappet faced vulture nests. The main objectives of the study were: 1) to obtain basic breeding information of lappet-faced vulture in Lochinvar National Park and the Kafue Flats in general, 2) to determine size of the breeding population in the National Park, 3) todocument distribution of the nesting sites, 4) tofacilitate development of a monitoring programme that would secure the nesting sites from human disturbance, and 5) to determine availability of suitable nesting sites and major threats that may interfere with breeding. Tree species on which nests were found were identified and height of nest above ground was estimated. A total of 22 nests were recorded with 5 (23%) being lappet faced vulture nests on seven species of trees. The mean height for nest placamenet was10 mabove ground. Host tree physiognomy, size and height were important characteristics in nest placement. Large trees of 10mand above are critical in facilitating nest placement and must be protected in identified breeding sites.

Position of Blackbird (Turdus Merula) Nests in Orange Trees

Nest placement affects the risk of predation and determines the microclimate for incubation. We have analysed the nest placement of the blackbird nests and the temperatures at which they are exposed in an orange plantation from Eastern Spain. The data come from a 16.9 ha of an orange plantation. In this plot, nest searching techniques were applied. Nest placement and the temperatures at midday were recorded from a sample of 84 nests. Furthermore, a sample of 16 nests was used to determine the daily variation between 8:00 and 20:00 hours. We measured the nest height, tree height, and distance from the tree centre to the nest, and the length of the longest branch. The temperatures inside the nest cup and of the surrounding air temperatures were also obtained. The range of the orange tree height was 82-425 cm (mean = 234.0 cm). The length range of the longest branch was 11-311 cm (mean = 136.4). The nests were placed at heights between 41 and 223 cm (mean = 134.4) and the distance from the centre of the tree varied from 8 to 233 (mean = 126.5). There was no variation in the nest heights and distances from the trunk to the nest place as the breeding season progresses. The air temperature (Tat) and the nest temperature (Tict) at midday increases as the breeding season progresses but the difference between Tat and Tict did not vary according to the time in the breeding season. The daily difference between the air and the nest temperatures increased from 08:00h to 12:00h and then decreased. Only three nests out of the 100 nests sampled were successful inbreeding.

Nest Survival, Predators and Breeding Performance of Booted WarblersIduna caligatain the Abandoned Fields of the North of European Russia

We examined breeding performance and the nest survival of Booted Warbler Iduna caligata on abandoned fields in Vologda region, Russia. We modelled daily survival rates (DSR) using data on 250 nests found in 2002-2011. We compared relative effects of year, nest age, date, weather conditions and nest placement characteristics. Clutch size did not vary over the study period and was on average 5.69 ± 0.04 eggs. Inter-seasonal variability was the most important component of DSR variation. The top model included a year effect, a quadratic nest age term and an interaction between year and quadratic age. Overall nest success varied greatly from 0.03 in 2008 to 0.7 in 2007. Nest height was an important nest placement covariate, nest remoteness from villages and roads were not influential. We detected the species composition of predators by watching nests of Booted Warblers and other grassland passerines as well as by observing the artificial nests. The main predators were carnivorous mammals, Common Viper Vipera berus, Harriers and corvids. Predator pressure was the main factor that determined nest success of Booted Warblers. Intra- and inter-annu- al fluctuations in the activity of predators may cause corresponding changes in nest success of Booted Warbler.

Evolution of Nesting Height in an Endangered Hawaiian Forest Bird in Response to a Non‐Native Predator

The majority of bird extinctions since 1800 have occurred on islands, and non-native predators have been the greatest threat to the persistence of island birds. Island endemic species often lack life-history traits and behaviors that reduce the probability of predation and they can become evolutionarily trapped if they are unable to adapt, but few studies have examined the ability of island species to respond to novel predators. The greatest threat to the persistence of the Oahu Elepaio (Chasiempis ibidis), an endangered Hawaiian forest bird, is nest predation by non-native black rats (Rattus rattus). I examined whether Oahu Elepaio nest placement has changed at the individual and population levels in response to rat predation by measuring nest height and determining whether each nest produced offspring from 1996 to 2011. Average height of Oahu Elepaio nests increased 50% over this 16-year period, from 7.9 m (SE 1.7) to 12.0 m (SE 1.1). There was no net change in height of sequential nests made by individual birds, which means individual elepaios have not learned to place nests higher. Nests ≤3 m off the ground produced offspring less often, and the proportion of such nests declined over time, which suggests that nest-building behavior has evolved through natural selection by predation. Nest success increased over time, which may increase the probability of long-term persistence of the species. Rat control may facilitate the evolution of nesting height by slowing the rate of population decline and providing time for this adaptive response to spread through the population.

Do age and type of plantings affect turtle dove Streptopelia turtur nest placement in olive agro-ecosystems?

Seventy active turtle dove nests were found in the Tadla irrigated olive agro-ecosystem, 39 in olive orchards and 31 in olive hedgerows. A two-way multivariate analysis of variance (MANOVA) was performed to determine the combined effects of olive age categories (class A < 10 years, class B 10–20 years and class C 21–30 years) and type of plantings (orchards and hedgerows) on nest placement within-tree. Results indicated that turtle doves' nests are placed higher up gradually as the trees are older. Nonetheless, the nest's relative vertical position in the canopy does not change from one age to another. Nest placement in the canopy was higher in hedgerows than in orchards. This game species exhibits adaptive behavioural plasticity in nest placement and appears well-adapted to olive grove conditions in this region. This high adaptability is beneficial to maintaining the species in these highly frequented man-made environments.

Snowy plover nest site selection, spatial patterning, and temperatures in the Southern High Plains of Texas

AbstractSnowy plover (Charadrius nivosus) populations have declined throughout their range, in part because of habitat degradation and poor nest success, making information regarding regionally specific nest site selection and spatial patterns important when considering habitat conservation and management guidelines. We determined nest site selection characteristics (n = 180) and examined spatial patterns (n = 215) of snowy plover nests in saline lakes in the Southern High Plains (SHP) of Texas. At 104 nests, we examined the influence of substrate type on nest temperatures and heat mitigation. Snowy plover nests were more likely to be found near an object, on pebble substrate, and with fewer plants than random sites. High use areas were generally located in areas with pebble substrate and on human‐made or natural islands, berms, and peninsulas. Overall, nests placed on pebble substrate had lower temperatures during the day than nests placed on sand substrates. Nest placement on pebble substrate may be valuable to nesting snowy plovers, providing thermal advantages to incubating adults and depressing potentially high nest predation rates. Management guidelines for this region should emphasize the importance of addressing key elements of snowy plover nesting habitat including the presence of pebble substrate and reducing vegetation encroachment. © 2012 The Wildlife Society.

Habitat and nest placement of Red-backed Shrikes Lanius collurio breeding in clear-cuts in southern Norway

Information on habitat, nest placement, phenology and clutch size in Red-backed Shrikes Lanius collurio was collected from a total of 71 nests in southern Norway during 1995–2009. In this area, which is situated at the north-western limit of the species’ distribution, breeding was predictable in clear-cuts in pine Pinus sylvestris forest where junipers Juniperus communis made up a large part of the shrub layer. This contrasts with previous descriptions of typical shrike habitat in clear-cuts which focused on the availability of young spruce Picea abies trees. Nests were almost exclusively located in Junipers (92%), further emphasizing the importance of this bush species as part of the shrike habitat in the study area. Mean nest height was 113 cm (range 0–250 cm) and increased with height of the nesting bush (mean = 225, range 120–400 cm). However, this increase was lower than expected if the relationship was simply proportional, indicating that the birds prefer to place their nests low in the vegetation even if higher alternatives are available. Clutch size ranged from 1 to 7 eggs (mean = 5.1) and estimated dates of first eggs varied from 10 May to 16 June (median = 3 June). Breeding time varied significantly between years but there was no correlation between breeding time and clutch size. Both height of nest and height of the nest bush increased significantly with breeding season, and possible reasons for these findings are discussed.

Nest, Eggs, and Nest Placement of the Brazilian Endemic Black-bellied Seedeater (Sporophila melanogaster)

We present the first detailed description of the nest and eggs of the Black-bellied Seedeater (Sporophila melanogaster) based on observation of 64 nests in three areas of grassland in southeastern Santa Catarina and northeastern Rio Grande do Sul states, Brazil. The nests were found from November through March. The nest has the shape of a shallow basket, constructed with portions of dried grasses and strung with spider webs. Half of the nests were constructed in Ludwigia sericea (Onagraceae), and the other half were in 15 other plant species. Of these, the most important were Eupatorium polystachyum (10%) and Achyrocline vauthieriana (6%) (Asteraceae). Only the female constructs the nest. The eggs are ovoid and colored whitish with brownish-purple spots near the wider portion. Clutch size was two eggs, rarely three.

Patterns of nest placement in a population of Marsh Tits Poecile palustris

The factors influencing nest placement by territorial birds are not fully understood, including the roles played by habitat, conspecific attraction and female experience of a previous nesting location. We used 7 years of Marsh Tit (Poecile palustris) nest-site and territory data, and high-resolution vegetation models derived from remote sensing, to investigate spatial patterns of nest placement with regard to previous female experience and age, conspecific attraction, and habitat in a woodland environment. We found no evidence for an effect of conspecific attraction or previous nest location on nest placement within the territory. However, first-year (FY) females placed nests in a random spatial pattern within their territories, and after first-year (AFY) females predominantly placed nests within the central parts of their territories, away from conspecifics. The core area of each breeding territory was centred on a region of comparatively taller overstorey and less understorey than other parts of the territory. Nest-sites were situated in localised areas of a similar structure, although absolute differences between selected and non-selected areas of the territory were not substantial. Both female age groups nested in areas of the territory where the overstorey contained relatively more Common Ash (Fraxinus excelsior) and Field Maple (Acer campestre), which may have been related to tree height, but there was no selection for English Oak (Quercus robur). We found no significant habitat differences between the territories of FY and AFY females that explained their differing patterns of nest placement.

Nest-site selection in the Canada Warbler (Wilsonia canadensis) in central New Hampshire

Reproductive success in birds is largely influenced by nest-site selection. Nest predators are the greatest source of nest failure for most species of birds. Species that nest on the ground may be particularly adapted to maximally conceal nests to reduce the risk of loss to predators. Little is known about nest-site selection in the Canada Warbler ( Wilsonia canadensis (L., 1766)), a small ground-nesting Neotropical migrant. We predicted higher amounts of vegetative cover at successful nests of Canada Warblers compared with unsuccessful nests because detection by predators would decrease with greater cover. We measured vegetative characteristics (concealment, stem densities, ground cover) around each nest and compared these variables between successful and unsuccessful nests and between actual nests and mock nest sites on and off territories. Greater concealment and higher stem densities were the main features surrounding a successful nest site. Nest sites had significantly greater concealment when compared with both random mock nest sites on and off territories. Thus, concealment is important for this ground nester and achieved primarily through thick cover and strategic nest placement in vertical substrate with an inconspicuous opening to the nest cup. Forests with complex ground structure and thickets of small-stemmed woody plants should be targets of conservation when considering how to manage this declining species.

Nest site selection and nesting biology of Rock Ptarmigan Lagopus muta japonicus in Japan

Capsule The population of Rock Ptarmigan in Japan have the southernmost distribution of Rock Ptarmigan in the world; they nest in moderately open sites which facilitate the detection of predators. Aims To assess nest site selection of this population of Rock Ptarmigan and to compare the data with those for other populations of this species. Methods Nest site characteristics were recorded and compared with random sites. Nest success, clutch size, and hatching rate were determined. Results All nests (n = 24) were found in Pinus pumila shrubs. Vegetation height at nests was significantly lower than at random sites. While the nests were well concealed, one direction of lateral cover was moderately open and its cover was significantly less than at random sites. Such nest placements may provide a good view from the nests, facilitating the detection of predators. Nesting success was 75.3% in 2006 and 61.1% in 2007, which is higher than reported in other populations of this species. Conclusion Rock Ptarmigan selected P. pumila shrubs with moderately open sites for their nests. We propose that these nest characteristics are related to nesting predation. Selection of nesting sites may depend on several factors. We suggest how this information can be used to guide conservation measures for this and perhaps other populations of Rock Ptarmigan. The population in Japan are at risk of extinction due to global warming and/or habitat loss.

Effects of spatial disturbance on common loon nest site selection and territory success

AbstractThe common loon (Gavia immer) breeds during the summer on northern lakes and water bodies that are also often desirable areas for aquatic recreation and human habitation. In northern New England, we assessed how the spatial nature of disturbance affects common loon nest site selection and territory success. We found through classification and regression analysis that distance to and density of disturbance factors can be used to classify observed nest site locations versus random points, suggesting that these factors affect loon nest site selection (model 1: Correct classification = 75%, null = 50%,K = 0.507,P &lt; 0.001; model 2: Correct classification = 78%, null = 50%,K = 0.551,P &lt; 0.001). However, in an exploratory analysis, we were unable to show a relation between spatial disturbance variables and breeding success (P = 0.595,R2 = 0.436), possibly because breeding success was so low during the breeding seasons of 2007–2008. We suggest that by selecting nest site locations that avoid disturbance factors, loons thereby limit the effect that disturbance will have on their breeding success. Still, disturbance may force loons to use sub‐optimal nesting habitat, limiting the available number of territories, and overall productivity. We advise that management efforts focus on limiting disturbance factors to allow breeding pairs access to the best nesting territories, relieving disturbance pressures that may force sub‐optimal nest placement. © 2011 The Wildlife Society

Genetic Parentage and Local Population Structure in the Socially Monogamous Upland Sandpiper

Abstract. For a single lineage of birds, the diversity of mating systems and parental care among shorebirds (Charadrii) is high, which has made them an important group for investigations of the evolution of social mating systems. From 2003 to 2007, we studied a population of the Upland Sandpiper (Bartramia longicauda) at Konza Prairie Biological Station in northeastern Kansas. Our objectives were to determine the genetic mating system of this socially monogamous shorebird and to determine whether spatial patterns of philopatry and nest placement might affect opportunities for extra-pair mating. We used six microsatellite markers to estimate rates of extra-pair paternity in 58 family groups (107 parents, 184 offspring). We found that 30% of broods contained extra-pair offspring, representing 15% of chicks, the highest rate of extra-pair paternity ever reported in a socially monogamous shorebird. High rates of extra-pair paternity were not due to the degree of relatedness between partners in mated pairs, an...

Hierarchical cues in brood parasite nest selection

Numerous hypotheses have been developed to explain how a brood parasite selects a host nest into which it lays its eggs. Most hypotheses address various aspects of nest placement. We used an extensive dataset to tease apart the relative strength of various hypotheses associated with nest placement and timing. These data were from North American tallgrass prairie and included nearly 2,000 nests of 17 host species known to accept eggs of the brood parasitic Brown-headed cowbird Molothrus ater. Regression tree analyses, with host species as a categorical covariate built around successive logistic regressions, implied that the “edge effect” and “perch proximity” hypotheses, the latter assessed as distance to woody vegetation, received the strongest support. Hypotheses concerning nest height, livestock proximity, habitat density, nest exposure, laying date, and host clutch size received weaker or subsidiary support, the latter meaning that the hypotheses received significant support only after edge effects or distance to woody vegetation were accounted for first. Host species was associated significantly with parasitism rate, but host species was itself correlated with various vegetation and landscape variables that we assessed. Brood parasitism rate and nest height were associated non-linearly. In addition to a clear hierarchical pattern among factors associated with rates of parasitism, several key explanatory variables had marked interactions, such as prairie edge and extent of woody vegetation or nest height and nest exposure. Such interactions, including between host species and certain landscape and vegetation variables, such as nest height and distance from woody vegetation, suggest caution is warranted when assessing the various competing hypotheses, which are not mutually exclusive.

Nests, Nest Placement, and Eggs of Three Philippine Endemic Birds

We describe the nest and eggs of two Philippine endemic passerines, the Rusty-faced Babbler (Robsonius rabori) and the Blue-breasted Blue Flycatcher (Cyornis herioti). We also describe a novel type of nest and nest placement for the Short-crested Monarch (Hypothymis helenae), and provide the first description of the eggs of this species. We discuss similarities among eggs and nests of these species with their relatives, and the need for more information regarding natural history and breeding habits for the Philippine avifauna.

Using Spatial Point-Pattern Assessment to Understand the Social and Environmental Mechanisms that Drive Avian Habitat Selection

ABSTRACT. Understanding when species distributions should be ascribed to patterns in the physical habitat, rather than to the influence of social cues, is a crucial step in understanding avian habitat selection. To distinguish between these mechanisms, we assessed the point pattern of 213 Saltmarsh Sparrow (Ammodramus caudacutus) nests and the spatial autocorrelation of vegetation characteristics at two study sites. Our tests of aggregation at cumulative and discrete distance classes failed to detect any significant nonrandom pattern, which is consistent with the hypothesis that nest placement is random with respect to other nests. When the timing of nesting attempts was taken into account such that only previous or currently active nests were considered, there was still no evidence that females attempted to nest closer to other nests than expected given random site selection. The underlying spatial structure of the vegetation variables was somewhat patchy, but not in a way that was consistent between sit...