Using community-based interviews to determine population size, distribution and nest site characteristics of Pallas's fish eagle in north-east Bangladesh

Pallas's fish eagle Haliaeetus leucoryphus was recategorized from Vulnerable to Endangered on the IUCN Red List in 2017 because of evidence that there is only a single population, which is declining as a result of continuous, widespread loss and degradation of freshwater wetlands. To determine the species’ status in Bangladesh, we conducted a large-scale community-based interview survey in north-east Bangladesh in 2017–2020. We also examined nest site habitat characteristics through field surveys and remotely sensed data. We conducted a total of 955 interviews in an area of 4,150 km2, through which we were able to determine the presence of 53 breeding pairs at a mean density of 1.2 nests per 100 km2. There was a higher nest density (3.7–4.8 nests per 100 km2) in some locations, which we identify as priority conservation areas. The majority of nests (62.2%) were close together and on tall trees with an open canopy structure. Nests were located within or close to (< 100 m) human settlements, and within 500 m of wetlands and rivers. Felling of nest trees, removal of nests by local people and loss of permanent wetlands (14.6% during 2010–2020) appeared to be the main threats. High nesting density in our study area suggests that the freshwater wetlands in north-east Bangladesh possibly hold the largest population of Pallas's fish eagle globally.

Long-Term Coexistence of Two Invasive Vespid Wasps in NW Patagonia (Argentina)

In Patagonia (Argentina) two non-native vespid wasps became established in the last decades. Vespula germanica was first detected in 1980 while V. vulgaris arrived some 30 years later. Both species can have a strong negative impact on agriculture, natural environment and on outdoor human activities. Invasion success -the establishment and spread of a species- may be influenced negatively by the degree of interaction with the resident native community, and alien species already present. The sequential arrival of these two wasps allows us to understand key questions of invasion ecology. Additionally, recognizing the outcome of the invasion by vespids in Patagonia -a region lacking native social wasps-, may help plan species-focused mitigation and control strategies. We explored long term species coexistence through the deterministic Lotka-Volterra competition model, using site-specific field data on prey captured (to estimate niche overlap) and current nest densities in sites. Food items carried by workers were similar but there is some degree of segregation. V. germanica nest density in shared sites, and in sites without coexistence, were 3.14 and 3.5 respectively, being higher for V. vulgaris with 4.71 and 5.33. The model predicts stable co-existence of both species in the invaded range, yet a higher abundance of V. vulgaris should be expected. Added to evidence on other foraging behavioral attributes of both wasp species and the invasion patterns observed in other regions, it is likely that the prior presence of V. germanica does not contribute significantly to the biotic resistance of the invaded range for V. vulgaris

Nest Characteristics of the Sumatran Orangutan (Pongo abelii) in the Wildlife Sanctuary Soraya Station in Aceh Province, Indonesia

Orangutans (Pongo spp.) populations used to be widely distributed throughout Southeast Asia, from Java in the south to the Southern China in the north during the Pleistocene. Their populations have declined up to 75% of their original size and are now distributed only in parts of the tropical rainforests of Borneo and Sumatra. Pongo pygmaeus, Pongo tapanuliensis and Pongo abelii are the three most representative species, in this study, here we discussed the latter. Sumatran forests are generally suffering from deforestation with rates ranging from 3.74% to 49.85% between 2000 and 2012. Thus, human wildlife conflict intensity has escalated and gained more traction. Orangutans are known as arboreal great apes and need to build nests for resting. We applied the transect line method (three transects; each 1,000 m long) at different elevations in Soraya Research Station, Gelombang Village, Sultan Daulat sub-district, Subulussalam district, and assessed the nest characteristics. The characteristics are: (1) nesting position referring to the position of nest on a tree; (2) nest successional stages defining the age and leaf decay used in constructing a nest indicated with I (new) until V (almost gone); and (3) nest density to predict the density of nest per square km. Afterwards, the identified nesting trees along the transect were further identified based on their species, and assessed based on three characteristics (the tree height, diameter and the height of a nest measured from the soil). A total of 27 nests were found, and 44% were located in transect III or at the riparian. Out of 27, four orangutans’ nests were found on Moraceae (Streblus elongatus) and Myrtaceae (Syzigium spp.), while three nests were found on Dipterocarpus sp. The tree height, tree diameter and nest height were 10 m–25 m (mean = 17.5 m; SD = ± 0.25), 10 cm–30 cm (mean = 20 cm; SD = ± 0.4) and 16 m–20 m (mean = 18 m; SD = ± 0.35), respectively. Meanwhile, nest density calculated based on the form: d = [N/ (L* 2w)], and the values obtained were 8.4, 13.45, 26.9 nests/km2 located on transect I, II and III or at the riparian. The most commonly found nest successional stages and position were stage III and position 3, respectively. This study could serve as a baseline research in primate conservation and nest characterisation could be used as guidance for any future activity planning (e.g. tree reforestation) in a particular region and the existence of various tree species diversity are indispensable for maintaining orangutan habitats’ quality.

Red wood ants in Bulgaria: distribution and density related to habitat characteristics

The only National Inventory of red wood ants in Bulgaria was carried out about 50 years ago (1970–1973). Formica rufa Linnaeus, 1761, F. pratensis Retzius, 1783, F. lugubris Zetterstedt, 1838 and F. polyctena (as F. polyctena x rufa hybrid) were found in a current monitoring programme. This study presents data on their current distribution and nest density, and provides more details about the habitat requirements for conservation purposes. Field studies were carried out by the transect method along the main mountainous areas in Bulgaria. We found 256 nests of red wood ants along 172 transects. The most abundant species was F. lugubris, followed by F. rufa and F. pratensis. Among the environmental variables, the elevation, exposure, ecological groups of plants, stone cover, grass cover, canopy cover and forest age appeared as significantly related to the presence and nest density of red wood ants.

Nest density drives productivity in chestnut-collared longspurs: Implications for grassland bird conservation

Grassland birds are declining faster than any other avian guild in North America and are increasingly a focus of conservation concern. Adaptive, outcome-based management of rangelands could do much to mitigate declines. However, this approach relies on quantitative, generalizable habitat targets that have been difficult to extrapolate from the literature. Past work relies heavily on individual versus population response, and direct response to management (e.g. grazing) versus response to outcomes. We compared individual and population-level responses to vegetation conditions across scales to identify quantitative targets of habitat quality for an imperiled grassland songbird, the chestnut-collared longspur (Calcarius ornatus) in northern Montana, USA during 2017–2018. We estimated nest density and nest survival within 9-ha survey plots using open N-mixture and nest survival models, respectively, and evaluated relationships with plot- and nest-site vegetation conditions. Plot-scale conditions influenced nest density, whereas nest survival was unaffected by any measured condition. Nest-site and plot-scale vegetation measurements were only weakly correlated, suggesting that management targets based on nest sites only would be incomplete. While nest survival is often assumed to be the key driver of bird productivity, our results suggest that nest density and plot-scale conditions are more important for productivity of longspurs at the core of the breeding distribution. Habitat outcomes for grassland birds should incorporate nest density and average conditions at scale(s) relevant to management (e.g. paddock or pasture).

Feral pigeons as a nest competitor for a small seabird

Due to their life-history traits, the petrels are particularly sensitive to predation by introduced species. Therefore, many populations have constricted their original breeding distribution range, currently only occupying predator-free sites. In this scenario, interspecific competition for nesting sites can be detrimental for the petrel’ conservation. Here, we evaluate how the presence of introduced mammals (cats Felis catus and rats Rattus spp.) and potential competitors for nest sites (Cory’s shearwaters Calonectris borealis and feral rock pigeons Columba livia) shape the distribution, breeding density, and breeding performance of the Bulwer’s petrel Bulweria bulwerii on Tenerife, the largest and most densely populated of the Canary Islands. We estimated nest density, assessed the role of nest location and nest characteristics on breeding success, and determined causes of breeding failure by exotic predators and competitors. Nest density was higher in predator-free colonies on marine rocks. Cat presence was the best predictor for nest density, while presence or abundance of competitors had no correlation to nest density. Breeding success varied between years and colonies, but was not related to nest characteristics. Of the unequivocally determined causes of breeding failure, pigeon competition for nests was the most frequent (7.3%), followed by rat predation (6.3%). We also compared petrel and pigeon nest cavities and found a considerable overlap in nesting niche. Our study provides insight on an overlooked impact of the invasive rock pigeon: nest competition with small seabirds. We encourage more research on the effects of pigeons on nest density, disease and pathogen transmission, and vegetation changes within petrel colonies.