Nest Trees Research Articles

Introduction pages

Notulae Scientia Biologicae (http://www.notulaebiologicae.ro), Issue 1, Volume 13, 2021: The papers published in this issue represent interesting novelties in different topics of life science. Among the exciting researches or reviews, we invite readers to find news about: Phytochemistry and pharmacological activities of Saponaria officinalis L.; The Spanish chamomile (Anacyclus pyrethrum) and pyrethrum (Tanacetum cineraiifolium): organic and natural pesticides and treasure of medicinal herbs; Prophylactic effect of the aqueous extract of Pimpinella anisum on the behavior of Wistar rats exposed to mercury; Anti-ulcer property of methanol fraction of Callichilia subsessilis leaf extract in albino rats; Nesting tree selection by scattered heronry birds of drought prone Northern Bankura, West Bengal, India: preference of Phoenix sylvestris near wetland-associated habitats; Explants selection for in vitro propagation of Pachyrhizus erosus L.; Silene thymifolia Sibth. et Sm. (Caryophyllaceae) – A vulnerable species in Romania: Anatomical aspects of vegetative organs.
 
 Announcement: From Volume 13, Issue 1, 2021, Notulae Scientia Biologicae journal will use article numbers in place of the traditional method of continuous pagination through the volume. This step helps us to maintain a rapid, efficient production process by being able to define pagination as soon as a paper is accepted.
 For papers that use article numbers, the page number of full-text articles will start from 1 to the last page and the citation needs only to list the article number, consequently, instead of the classic style of the journal citation.

Natural insecticides for the control of urticating ant, Tetramorium aculeatum Mayr (Hymenoptera: Formicidae) in a coffee plantation of Southwestern Ethiopia

Coffee, Coffea arabica L. is a vital crop in Ethiopia's social, cultural, and national economy. Despite its dominant role in the country, the crop is challenged by various insect pests, which reduce coffee yield and quality. The urticating ant or biting ant, Tetramorium aculeatum Mayr (Hymenoptera: Formicidae), is an important pest in coffee that affects farming activities in Southwestern Ethiopia. The objective of this study was to evaluate the efficacy of some natural insecticides for the control of biting ants. Nine insecticide treatments were evaluated both under ex-situ and in-situ conditions in CRD and RCBD designs, respectively. Under the ex-situ evaluation, all the insecticide treatments caused significantly higher mortality of biting ants and caused complete mortality within 24 h. Under field conditions, the insecticides showed significant variations in the percent of evacuated nests, and the number of newly constructed nests. In both efficacy tests of ex-situ and in-situ experiments, the mortality of biting ants and percent of evacuated nests in the coffee trees treated with oxymatrine and nimbicidine were found to be comparable and effective as the deltamethrin 2.5% EC. All the insecticide treatments significantly reduced the number of newly constructed nests compared to the control plot. On the other hand, deltamethrin 2.5% EC significantly decreased newly constructed nests after 30 days of application compared to the other insecticide treatments. Generally, the natural insecticides effectively minimized the biting ant infestation, but further studies are essential on the frequency of spray to use them for sustainable management approaches of biting ant in the coffee plantation.

Nesting tree selection by scattered heronry birds of drought prone Northern Bankura, West Bengal, India: preference of Phoenix sylvestris near wetland-associated habitats

The present study was conducted in the Gangajalghati block of Northern Bankura, India, to investigate the habitat and nest tree preference of three colonial waterbirds viz. Nycticorax nycticorax, Egretta garzetta, and Ardeola grayii. The study sites were surveyed for 20 months between 2017 and 2020. A total of 817 nests with an average of 204 per year were recorded on 13 tree species. Nycticorax nycticorax showed the maximum nest count followed by Egretta garzetta and Ardeola grayii. Relative abundance data revealed Phoenix sylvestris as the most abundant species (45%) of the area and harbours the highest proportion (33%) of nests. Pooled nest count data showed significantly higher (p < 0.01) total nest counts in the wetland associated habitats than others. The study observed more nest density of all three species near a cluster of small ponds than in a large water body. Year-wise difference in cumulative nest number and mean nest abundance of all three species was statistically insignificant. The interspecific nearest neighbour on Phoenix sylvestris were Egretta garzetta (88.37%) for Nycticorax nycticorax and Nycticorax nycticorax (83.25%) for Egretta garzetta and Ardeola grayii. Further, the study evaluated the impact of two tropical cyclones (Amphan and Fani) on the total nest count and found that more than 75% nests (p < 0.05) were destroyed by the mighty Amphan in May 2020. The study provides a baseline data on nesting trees and habitat preference of three species of heronry birds from Northern Bankura.

Fine-scale genetic structure reflects limited and coordinated dispersal in the colonial monk parakeet, Myiopsitta monachus.

The genetic structure of animal populations has considerable behavioural, ecological and evolutionary implications and may arise from various demographic traits. Here, we use observational field data and molecular genetics to determine the genetic structure of an invasive population of monk parakeets, Myiopsitta monachus, at a range of spatial scales, and investigate the demographic processes that generate the observed structure. Monk parakeets construct large nests that can house several pairs occupying separate chambers; these nests are often aggregated within nesting trees. We determined patterns of relatedness within compound nests, within nesting trees and between trees. Spatial autocorrelation analyses of pairwise genetic relatedness revealed fine-scale genetic structure with relatives of both sexes spatially clustered within, but not beyond, nesting trees. In addition, males were more related to males sharing their compound nests than to other males occupying the same nesting tree. By contrast, males and females within compound nests were not significantly more closely related than elsewhere in the same tree, and we found no evidence for inbreeding. Adults showed high breeding site fidelity between years despite considerable disturbance of nest sites. Natal dispersal was female-biased, but dispersal distances were relatively short with some natal philopatry observed in both sexes. Sibling coalitions, typically of males, were observed amongst both philopatric and dispersing birds. Our results show significant clustering of kin within compound nests and nesting trees resulting from limited and coordinated natal dispersal, with subsequent breeding site fidelity. The resulting genetic structure has implications for social behaviour in this unusual parrot species.

Relationship between lake area and distance from the city centre on lake-dependent resident and migratory birds in urban Bangalore, a tropical mega-city in Southern India

Abstract Urbanization is one of the major causes of biodiversity loss worldwide. Some species are able to adapt to urbanization, whereas others perish. Studies on long-term effects of the impact of urbanization on species diversity and abundance patterns are especially lacking from tropical cities. We seek to assess the relationship between urbanization and species richness of lake-dependent birds in Bangalore, a tropical mega-city in Southern India. We specifically ask: (i) How is bird species richness related to the size of the lake? (ii) How is bird species richness in Bangalore’s lakes related to the degree of urbanization? We used data from 2014 to 2019, collected from eBird—an online database that collates information on bird observations globally. Both lake area and distance from the city centre are correlated to species richness, with larger lakes supporting more bird species. As distance from the city centre increased (i.e. urbanization decreases), bird richness increased. Overall, in the city of Bangalore, migratory birds have declined while many lake-dependent resident birds seem to be increasing over the past 5 years. We hypothesize that birds that roost and nest in trees appear to be increasing. To confirm this, further research taking a trait-based approach is required. Urbanization appears to have species-specific impacts on lake-dependent birds in this tropical city, with certain groups of birds faring better than others. This research adds to the significant paucity of studies of the impact of urbanization on biodiversity in the urban tropics.

Breeding behaviour and diet of Rufous Owls Ninox rufa in the Darwin Botanic Gardens

The breeding cycle of a pair of Rufous Owls Ninox rufa was observed over five breeding seasons, 2016–2020, in the Darwin Botanic Gardens, Northern Territory. A pair failed or did not breed in four of those years and raised one fledgling in 2018. The Owls occupied a hollow 2.5 m above ground in the trunk of an exotic Earpod Tree Enterolobium cyclocarpum. In 2018, laying occurred sometime between 11 June and 2 July, hatching between 21 and 25 July, and fledging (first true flight) on 6 September, with branching on 2–5 September, giving a nestling period of 44–48 days. The juvenile remained dependent until mid November, giving an estimated post-fledging dependence period of 10 weeks. For the following 3 weeks, it roosted alone within its natal home range, increasingly far (270–320 m) from the nest tree and roosting adults. Calling behaviour (including duetting by the pre-laying pair), courtship, copulation and parental behaviour and routines are described. From observations and pellet analysis, the Owls’ diet consisted of 78% mammals [Common Brushtail Possums Trichosurus vulpecula arnhemensis, flying-foxes (probably all Black Flying-foxes Pteropus alecto) and rats (probably Black Rats Rattus rattus)] and 22% birds (passerines and non-passerines up to Orange-footed Scrubfowl Megapodius reinwardt in size) by number.

Predation and prey-caching of Eastern Water Skinks Eulamprus quoyii by nesting Nankeen Kestrels Falco cenchroides in eastern New South Wales

The breeding diet of a pair of Nankeen Kestrels Falco cenchroides nesting in Beresfield, eastern New South Wales, in 2020 was investigated. By individual prey species, the diet comprised 61.3% reptiles (including two prey species not previously recorded in the Nankeen Kestrel diet—Eastern Water Skink Eulamprus quoyii and most likely Southern Rainbow Skink Carlia tetradactyla), 9.7% birds (including a new prey species—Superb Fairy-wren Malurus cyaneus), 6.4% invertebrates (two crickets: Grylloidea), 3.2% mammals (one House Mouse Mus musculus) and 19.4% unidentified prey items (percentages by number). During 31.5 h of observations, the male delivered 22/31 prey items (71%) and the female delivered 9/31 prey items (29%) to the nest tree. The average delivery rate over the entire nestling period was one prey item per hour. Prey-caching, whereby the female stored lizards in the fork of a tree and later retrieved them and fed them tothe single nestling, was observed. Further studies are needed to obtain well-documented accounts of prey-caching by Australian falcons.

Do Structural Attributes of Trees Affect Nest Activity in the Black-Faced Ibis Theristicus melanopis?

The Black-faced Ibis Theristicus melanopis builds numerous nests in some trees but avoids others, suggesting that particular attributes of trees are selected for. In this study we test the hypothesis that the number of primary stems rising from the trunk correlates positively with the number of active nests in this colonial nesting species. Within an area of 61 km2 of pastures in southern Chile, in 2017 we selected 96 isolated trees. For each tree we examined nest presence and breeding status. Of the total number of trees examined, 38 had active nests. The active nests were built solely in Patagonian Oak Nothofagus obliqua and Chilean Laurel Laurelia sempervirens. The nests were mainly located on branches of the primary stems, at an average height of 13.87 ± 0.62 m (±SE; range: 2–27 m). The average number of active nests per tree was 0.82 ± 1.13 (range: 1–4 nests) and did not vary significantly between the two tree species. However, average nest height was significantly greater in the Patagonian Oak than in the Chilean Laurel. Partial least squares structural equation modelling (PLS-SWM) indicated that tree structure, determined by tree age and canopy height, canopy cover and concealment, contributed to explaining the number of active nests in the trees. There was no relation between the number of primary stems and the number of active nests. We conclude that the Black-faced Ibis responded to the general tree architecture when nest building and that, probably, the presence of an active nest in a given tree constitutes key intraspecific information that induces other individuals of the population to build their nests in the same tree.

Distribution and Characteristics of Javan Hawk Eagle Nesting Trees in Gunung Halimun Salak National Park, Indonesia

Javan Hawk Eagle is one of the three keys species of the Gunung Halimun Salak National Park and endemic to the island of Java. Protecting the active Javan Hawk Eagle nesting tree is one of the efforts to increase the success rate of Java Hawk Eagle breeding so that information on the distribution and characteris-tics of Javan Hawk Eagle nesting tree is needed. Field exploration was carried out to determine the existence of the Javan Hawk Eagle nest. There were 10 individuals of Javan Hawk Eagle nesting trees which consisted of 5 species namely Rasamala, Huru, Damar, Leng-sar and Manggong with tree architecture models of rauh, massart, scarrone and aubreville, tree height between 26-55 m and height of nests between 18-41m. The Javan Hawk Eagle nesting trees grow in primary, secondary, and plantation forests in a height between 670- 1295 masl, with a steep and very steep slope, the majority of the dis-tance from the river is less than 100 m and the majority of the dis-tance with ecotone is less than 600 m. Javan Hawk Eagle nest on Damar is the first finding at Gunung Halimun Salak National Park.

Suitable nesting sites for specialized cavity dependent wildlife are rare in woodlands

Non-excavating species that prefer rare combinations of cavity traits are limited to only a fraction of the available tree cavity resource. Understanding animal preferences and quantifying the abundance of suitable cavities is fundamental to protecting non-excavators. We aimed to identify the traits of trees and cavities selected by a vulnerable, non-excavating bird, the superb parrot Polytelis swainsonii. We also evaluated cavity abundance and the accuracy of ground-based survey techniques (where an observer estimated the number of cavities in the canopy with binoculars from the ground). We then climbed trees to accurately identify true cavities and to measure their internal dimensions. Ground-based counts of tree cavities were correlated with the true number of cavity entrances in trees. When trees had zero cavities, ground counts overestimated their abundance, but for cavity-bearing trees ground counts underestimated their abundance. We found that superb parrot nest trees contained more cavities than random trees. Superb parrots selected cavities that were deeper, with wider floors and entrance sizes than random cavities. Cavities with the combination of selected traits comprised only 0.5% of the standing cavity resource. Our results confirm that non-excavators can be very selective about the types of trees and cavities they use for nesting. Rarity of suitable cavities may be a factor limiting the population growth and recovery of superb parrots. Without accounting for the critical information gap between what is observed on the ground, and what is in fact present in trees, effective habitat management for non-excavators may be compromised by inaccurate assessments of cavity abundance and conservation status.

Nest-site selection by the white-tailed eagle and black stork \u2013 implications for conservation practice

BackgroundNesting trees and habitat represent the key factor underpinning stand selection by forest-dwelling birds. While two large European species – the black stork (Ciconia nigra L.) and white-tailed eagle (Haliaaetus albicilla L.) – are known to require old, large trees for nesting, we sought to investigate further by comparing species requirements at the levels of the nesting tree, nesting stand, and landscape. This entailed a detailed examination of forest features within circles of radius 15 m surrounding 16 and 19 trees holding the nests of storks and eagles respectively. The same parameters were also checked in the vicinity of 50 randomly-selected mature trees.ResultsOur results indicate different nesting preferences, with the eagles entirely confining themselves to Scots pine (Pinus sylvestris L.) – a species also chosen by black storks, which nevertheless regularly favour pedunculate oak (Quercus robur L.). Both species select trees of greater girth than the random ones, but white-tailed eagles choose to nest in the vicinity of patches of mature old stands with a loose canopy, to the extent that nesting trees and surrounding trees are of similar ages. In contrast, black storks prefer “veteran” trees with low-set crowns that are much older than any others in their vicinity. Nesting trees of the eagles are away from roads and close to lakes, while black storks do not avoid roads.ConclusionsAs the ages of nesting trees of both species are greater than ages at final cutting in this region’s managed forest, silvicultural measures will need to be adjusted, with small patches of forest spared, or larger areas as “islands” of old-growth. Likewise, as tending and thinning are engaged in, certain trees with horizontal branches will need to remain, with relict trees also left untouched. As it happens, all of these recommendations are anyway key elements of close-to nature silviculture and multifunctional forestry.

What can the abundance of Grey Parrots on Príncipe Island tell us about large parrot conservation?

AbstractWhile populations of the Endangered Grey Parrot Psittacus erithacus have collapsed across its range, the species remains remarkably abundant on the island of Príncipe, Gulf of Guinea. We examine how aspects of its ecology interplay with local environmental conditions, to inform conservation strategies for this species and other large parrots. On Príncipe, parrots breed in large trees of common species, with nest densities (42 ± 34 km−2) greatly exceeding those for any comparably sized parrot. Productivity is high (1.9 chicks per cavity), probably reflecting the absence of nest competitors and predators. Food sources are abundant and much of the island is inaccessible to trappers, so many nests are successful each year. Historically harvest has involved taking only chicks from trees in a few traditional patches. These conditions have combined to allow Grey Parrots to thrive on Príncipe, while elsewhere nest trees are timber targets, nest competition and nest predation are likely to be more intense, trapping is indiscriminate, and few areas remain unexploited by trappers. Preservation of large trees as breeding refugia, and vigilance against the indiscriminate trapping of adult birds, are identified as key conditions to stabilize and recover mainland Grey Parrot populations and indeed large parrots generally, given their very similar ecological traits and anthropogenic circumstances.

Comparison of Nesting Ecology of Three Co-Existing Atlantic Forest Woodpeckers Reveals Narrow Specialization in the Helmeted Woodpecker Celeus galeatus

The Atlantic Forest in southeastern South America is a biodiversity hotspot with high species richness and high forest loss. Three large to medium-sized woodpecker species (Robust Woodpecker Campephilus robustus, Lineated Woodpecker Dryocopus lineatus, and the globally threatened Helmeted Woodpecker Celeus galeatus) coexist in the south of the ecoregion, and show remarkable convergence in plumage patterns and colouration, possibly driven by interspecific interactions. We assessed differentiation in nest tree species, nest substrates, and timing of breeding and evaluated whether nesting ecology may be a factor explaining an association with mature forests in the Helmeted Woodpecker. Robust and Lineated Woodpeckers excavated cavities in nine and eight nest tree species, respectively, whereas Helmeted Woodpeckers specialized narrowly on laurel trees (88% of nest cavities in two species in genus Nectandra of 52 ± 14 cm DBH). Helmeted Woodpecker is further distinguished by a more frequent use of living, partially decayed trees and by more frequent re-use of nest cavities. When nesting in selectively logged forest (vs. old-growth), Robust and Lineated Woodpeckers used trees with smaller DBH and Robust Woodpeckers excavated lower in trees. Helmeted Woodpeckers selected nest trees with similar dimensions in both environments, indicating lesser flexibility. Helmeted Woodpeckers bred 20–23 days later in the year than Lineated and Robust Woodpeckers, potentially allowing them to avoid nesting near the two larger species. The narrow specialization of Helmeted Woodpecker on nesting in Nectandra trees of large sizes at the onset of decay is a possible factor in making it sensitive to selective logging effects. To stop declines of Helmeted Woodpecker we recommend (1) sparing large trees from selective logging (including Nectandra and tree species used for roosting), and (2) restoring more forested areas to mature forest conditions.

Do racket-tailed drongos make tree guards for their nest trees?

Abstract Greater racket-tailed drongos are renowned for their splendid mimicking abilities, and for their significant roles within mixed species flocks in the Old World tropics. Yet, we know little about their basic ecology and breeding behaviour. Here we describe a set of unique behaviours of these drongos during their nesting season. Racket-tailed drongos nested in trees in an open patch of forest, often returning to the same tree year after year. The nesting pair also smoothened the bark of the nest tree trunk with their beaks. These findings suggest that the nest tree is a crucial resource for this species, and have implications for the cognitive abilities of drongos, as well as for hitherto unknown interactions between an avian species and tropical forest trees.

Nest tree characteristics of Grey-headed Woodpeckers (Picus canus) in boreal forests

Nest tree characteristics of Grey-headed Woodpeckers (Picus canus) in boreal forests

Faunal input at host plants: Can camel thorn trees use nutrients imported by resident sociable weavers?

“Islands of fertility” result from the focussing of water and nutrients around many shrub or tree species due to plants foraging for resources. Plant–animal feedbacks may amplify the development of such islands through environmental modification due to, for example, faunal deposition of nutrients and seeds. Fauna residing within vegetation clumps are likely to exert stronger feedbacks on their hosts than itinerant species. We studied the interaction between camel thorn trees (Vachellia erioloba) and the colonial nests of sociable weavers (Philetairus socius) in the Kalahari. We hypothesized that the accumulation of biological material below the nests will alter the nutrient status of the soil beneath the nest trees, in relation to unoccupied trees and the surrounding grassland. We also suggested that this association will have both positive and negative effects on the camel thorn trees. We found that soil concentrations of N, P, and K were, respectively, 4, 4.6, and 1.2 times higher below trees with nests compared to control trees, indicating faunal concentration of nutrients. Soil δ15N values were higher below trees with nests than below control trees without nests. Foliar δ15N values were also higher in nest trees than in control trees, showing the trees accessed faunally derived N. Furthermore, foliar biomass per diameter of terminal branches was 27% higher in nest trees, suggesting that trees respond to nutrient input from the weavers with increased growth. Large barren areas in the subcanopy vegetation directly beneath the colonies were attributed to decreased water infiltration rates, as a result of accumulation of organic matter due to continuous deposition of feces, possibly limiting competitive species from establishing in the subcanopy. On the other hand, canopy volume was reduced in trees with nests due to nests occupying large volumes within the canopy, and nests frequently causing branch fall, indicating costs associated with hosting weaver colonies. Synthesis: We found nutritional benefits to camel thorn trees when hosting sociable weaver colonies. These benefits can potentially overcome important environmental constraints, but these are partially offset by the resulting costs to the host trees.

Harpy Eagle (Harpia harpyja) nest tree selection: Selective logging in Amazon forest threatens Earth's largest eagle

Characterizing wildlife conservation problems is essential to properly inform conservation planning, and requires detailed knowledge on critical life stages, such as reproduction. Large tropical raptors often require large emergent trees to build their huge nests. However, large emergents are also in heavy demand by the timber industry. Here, we review the literature to characterize nesting structures used by Earth's largest eagle, Harpy Eagles (Harpia harpyja) and examine to what extent nest-tree selectivity is targeted by selective logging. We show that Harpy Eagles selected specific forest canopy structures as nesting platforms. Nests were large (mean size 152 × 99 cm) and typically located on the main fork of 28 emergent tree species, 92.8% of which are commercially targeted by the timber industry. AIC-based stepwise regression indicated that, compared with non-nesting emergent trees, nest trees were 19.6% taller at the first bifurcation; had crowns 26.6% wider; had 33.3% fewer branches <45°, which were on average 35% lower-angled. Tree size varied widely across the range of nesting tree species, but peaked near the Equator, and were high-statured in unflooded forest compared with flooded forests. Our results show that commercial loggers target the same set of species and individuals on which Harpy Eagles nest, questioning whether large tracts of selectively logged Amazonian primary forests still provide suitable nesting habitat for this mega-raptor. We conclude that suitable Harpy Eagle nesting trees have been rapidly lost over the species last stronghold, and this information may prove useful to the upcoming species evaluation by IUCN.

An investigation of the monitoring and management of the habitat of the family Ardeidae in Muan Yongwol-ri Breeding Sites in Korea

The purpose of this study was to investigate the variation in populations and species of the family Ardeidae through an evaluation of environmental habitat characteristics in the breeding sites of the family Ardeidae in Muan Yongwol, Korea. The study area has been protected as a Natural Monument (No. 211) in Korea and is located in Yongwol, Muan, in Korea. The monitoring of the herons was performed in October 2015 and from February to September 2016. The monitoring of vegetation, fish, benthic macroinvertebrates, and amphibian was performed in April and July of 2016, and the monitoring of land insecta was conducted in July 2016. The populations of the Ardeidae family in the Muan Yongwol-ri habitat of egrets and herons were recorded as 840, 1155, 1211, and 52 for Ardea cinerea, Egretta alba, Egretta garzetta, and Nycticorax nycticorax, respectively. Bubulcus ibis was not found. Terrestrial insects were found in 10 orders, 62 families, and 142 species. Benthic macroinvertebrates were in 11 orders, 15 families, and 18 species, and the predominant species was Chironomidae sp. Fish were found in two orders, three families, and nine species, and Carassius auratus were dominant. The proportions of fish, amphibian, reptilia, insecta, and others for food of Ardeidae were observed at 56.9%, 20.2%, 6.4%, 14.7%, and 1.8%, respectively. The area of the nest trees of Ardeidae family was approximately 8805 m2. The nest tree counts of Pinus thunbergii, Quercus serrata, and Quercus acutissima in the breeding sites were 147, 3, and 3, respectively, and all dead trees were Pinus thunbergii. The levels of salinity and available phosphate were much higher in the breeding site of the Ardeidae family than they were in control area. A management plan should be followed in this breeding area, such as understory vegetation thinning, soil improvement, or transplanting nest trees.

Conserving nest trees used by cavity-nesting birds from endangered primary Atlantic forest to open farmland: Increased relevance of excavated cavities in large dead trees on farms

Understanding nest-site selection is critical to conserving tree-cavity-nesting wildlife, but nest-sites may vary across landscapes. We examine variation in the characteristics of trees and cavities used by cavity-nesting birds from globally-threatened primary Atlantic Forest to open farmland with isolated trees. We predicted that nests would occur in the largest trees available, but that secondary cavity nesters (non-excavators) would increase their use of bird-excavated cavities and dead and exotic trees in open farmlands. We used a stratified case-control design and 20 random plots to assess variation in characteristics of trees and cavities (used and available) across gradients of canopy cover and distance to forest edge in subtropical Argentina. For secondary cavity nesters, nest cavities were more likely to occur in larger-diameter trees across all stand conditions, but more likely to occur in dead trees as canopy cover declined (i.e., in open farmland; n = 123 nest trees). For primary excavators, nest cavities were more likely to occur in dead (vs. live) trees, with larger diameter, regardless of stand conditions (n = 54 nest trees). Available cavities declined from 4/ha in primary forest to 0.4/ha in open farmland. Cavities were increasingly of excavated origin in open farmland, including both available cavities and those used by secondary cavity nesters, which indicates that avian excavation may partly compensate for the loss of decay-formed cavities when large trees are cleared. As forest landscapes shift toward a predominance of agroecosystems, dead trees and primary cavity nesters may take on important roles in conserving cavity-nesting communities and their ecosystem functions. However, nest cavities declined in height and depth, and increased in entrance size toward open farmland, raising the possibility that birds increasingly use suboptimal cavities as forest cover declines.

Nest site selection by Loggerhead Shrike (Lanius ludovicianus) in a fragmented landscape

Understanding which factors influence nest site selection can lead to more effective species conservation. The Loggerhead Shrike (Lanius ludovicianus) has experienced severe declines since the 1940s and could potentially benefit from fine-scale management for nesting habitat, especially where fragmentation impedes conservation at the landscape scale. We examined how habitat characteristics at the nest tree and territory core scales influenced nest site selection by Loggerhead Shrikes in the coastal plain of South Carolina. We found 41 Loggerhead Shrike nests and measured habitat characteristics at the nest site and at available sites to model selection factors at the tree and territory core scales. Loggerhead Shrikes selected for low heterogeneity of vegetation density, high heterogeneity of vegetation height, and lower shrub and tree densities at the territory core scale. Loggerhead Shrikes also preferred nest trees with larger diameters at breast height. Overall, Loggerhead Shrikes appeared to select for nest site characteristics that enhanced foraging ease and success, and limited predation risk. We suggest that landowners in the southeastern coastal plain increase grassy habitat on their property and retain large trees in suitable nesting locations to increase optimal nesting habitat for Loggerhead Shrikes.