Occupied Nests Research Articles

Using a drone to monitoring arboreal nests of birds of prey

ABSTRACT The breeding parameters of birds are the key element of bird population monitoring. The assessment of nesting success is difficult in the case of arboreal nests, which are typical for birds of prey. Drones are valuable tools for monitoring arboreal nest occupancy. We tested the feasibility of safely monitoring the common buzzard Buteo buteo and northern goshawk Accipiter gentilis nests via drones. We compared assessments of nest occupancy and the number of fledglings in occupied nests using drones with those obtained from traditional ground-based observations. Additionally, the response of the raptors to drone appearance was documented. The assessments of the nest occupancy of the common buzzard from the ground level and the drone were not significantly different. The monitoring of nest occupation by drones was more precise for northern goshawks. Monitoring using drones showed a higher number of juveniles. Adult birds reacted weakly to the presence of the drone. Our study indicates that monitoring arboreal nests of birds of prey with drones is more effective than monitoring arboreal nests from the ground and does not elicit adverse reactions from the birds. Further studies should be conducted to determine the responses of other raptors.

Nesting Bald Eagle Population Numbers, Density, Territorial Resources, and Relationship to Human Development in Northern Colorado’s Front Range

To better understand the population of the Bald Eagle (Haliaeetus leucocephalus) nesting along northern Colorado’s Front Range, from 2016 to 2022 we studied 86 occupied nests within an area of 20,586 km2. From 2017 to 2020, 279 juveniles fledged from 237 nesting attempts in a smaller, main nest-study area with 68 nests. The nests’ success over these four years ranged from 52 to 70%, and their productivity varied from 1.1 to 1.3. The average nearest-nest distances for three discrete areas in the Front Range (5.03 to 7.26 km) are at least 2.8 to 4.0 times greater than these distances in four nesting populations in wetter regions but shorter than distances observed between nests in drier Arizona. In our study area the coverage of buildings within 400 m of Bald Eagle nests is relatively low by comparison to the coverage around randomly selected points, averaging 1344 m2; for 63% of the nests this coverage was less than 800 m2. We classified the 86 nest territories into eight categories that describe the dominant resource habitat and predicts the eagles’ reliance on Black-tailed Prairie Dogs (Cynomys ludovicianus) versus fish as prey. Predation on fish was predicted to be dominant at 51% (n = 44) of the nests, predation on prairie dogs at 32% (n = 28).

Nest Box Bacterial Loads Are Affected by Cavity Use by Secondary Hole Nesters.

Among the environmental factors that affect bird nesting in nest boxes, the influence of microbial communities is relatively poorly understood. In this study, nest boxes used for breeding by secondary cavity nesters were sampled before the start of the breeding season to assess the bacterial loads of the nest box in relation to their previous year status. Different parts of the wooden nest box offer variable conditions for the development of bacteria. During the breeding season, the nest box entrance hole is wiped out by birds, delivering bacteria to their bodies, but during winter, it is exposed to unfavourable external conditions. The interior of the nest box, in turn, is also wiped by birds, but the conditions during winter are more stable there. Therefore, samples from the entrance hole and the interior of the nest box were taken at two different study sites: an urban parkland and a natural forest. We predicted that both the occupancy of the nest boxes during the previous breeding season by birds and the nesting sites would influence the bacterial load of the nest box. To verify this prediction, two categories of nest boxes were sampled at both study sites: nest boxes occupied by any of the two tit species (Great Tit or Blue Tit) in the previous season for breeding and nest boxes that had remained empty that year. The interior bacterial load of the nest box was higher in the nest boxes occupied in the previous breeding season, but only in the forest area. Furthermore, the bacterial load of both the entrance hole of the nest box and the interior was significantly higher in the forest study area in both occupied and unoccupied nest boxes. Our results show that the bacterial load of the nest box is positively related to the presence of nests in the previous breeding season and can vary between different sites.

Abundance and Breeding Ecology of Critically Endangered Vultures in Mole National Park, Ghana

ABSTRACT Vultures are among the most threatened species in Africa, with several critically endangered species surviving mainly or only in protected areas. West African vulture declines are correlated with steep losses of natural habitat and mammalian wildlife. Major factors driving vulture extirpations include wildlife trade for traditional medicine, belief-based rituals, and bushmeat. Current data on vulture abundance and breeding ecology are crucial for conservation but lacking in many countries, including Ghana. Between 2020 and 2022, we conducted 761 km of surveys for critically endangered vultures in Mole National Park (Mole NP), a 4840 km2 protected savanna in northern Ghana. Using our count data, we estimated populations of 29–36 Hooded Vultures (Necrosyrtes monachus), 25–73 White-backed Vultures (Gyps africanus), and 3–4 White-headed Vultures (Trigonoceps occipitalis) in the southern region of Mole NP. We also documented 17 occupied vulture nests, including six Hooded Vulture nests, 10 White-backed Vulture nests, and one White-headed Vulture nest. Our findings include the first nest records for Hooded Vultures in Mole NP, the first nest description of White-backed Vultures in Ghana, and the first nest records for White-headed Vultures in Ghana, confirming the importance of Mole NP for conserving critically endangered vultures. Reducing poaching, preventing the killing of vultures for wildlife trade, and protecting vulture habitat and food resources will be paramount to the survival of critically endangered vultures in Ghana and West Africa.

Behaviour of native birds and analysis of vocalizations, in a small reforested urban space near downtown Goiânia, Goiás state, Brazil

Due to habitat loss, several bird species that are dependent on forest environments seek refuge in green spaces within cities. The objective this study was to verify if the afforestation with autochthonous fruit trees of a small urban space could provide enough resources as food, shelter, and substrate for nesting of autochthonous bird species. Between June 2020-May 2021, during the covid-19 pandemic we observed the activity of bird species that visited a small forested urban space in Goiânia, Brazil. We recorded the behavioural activities of the birds using the focal animal technique, recordings of vocalizations and photographic and video recordings. About thirty species of birds were seen visiting our small urban wooded space. The most conspicuous species were the Amazonian Motmot, Picazuro Pigeon, Ferruginous Pygmy-Owl, Rufous-Browed Peppershrike, Rufous-bellied Thrush, Yellow-chevroned Parakeet, Great Kiskadee, Blue and Yellow Macaws, and the Common Potoo. All these species rested, vocalized and took refuge in the small urban wooded space. We also observed some species that nested, and many others that fed on tree fruits, insects and earthworms. We verified the presence of Amazonian Motmots (Momotus momota) adapted to this environment when we saw adult and juvenile Motmots and found an active nest. We also verified the reproductive adaptation of the Picazuro Pigeon (Patagioenas picazuro) observing the courtship and mating behaviour and found an occupied nest, which corroborates with the reproductive adaptation of the Picazuro Pigeon. We emphasize that native fruit trees are a fundamental part of urban environments, as they guarantee food for frugivorous birds, whereas mature leafy trees provide conditions for nesting and allow birds to congregate and communicate.

Habitat suitability mapping of white stork Ciconia ciconia in one of its key European breeding areas

Due to rapid changes of the agricultural practice, the traditionally managed farmland became currently-one of the most endangered habitats in Europe. Species related to the rural landscape have been facing a great challenge of adaptation to quickly changing conditions. Therefore, recognizing and characterizing highly suitable areas for white storks is very important to plan conservation measures in the era of changes in agriculture and land use. Here, combining nest survey data (811 occupied nest), GIS-data on habitat availability and modelling approach, we characterize the current foraging conditions of the white stork Ciconia ciconia, an indicator of the agricultural habitat biodiversity and an umbrella species for organisms associated with agriculture landscape. The studied population breeds in the Warmińska Refuge Natura 2000 site (N Poland), one of the key breeding areas of this species in Europe. Breeding pair presence was predicted by the area of pasture, meadows, field ponds, and linear water within a 1 km buffer around the nest. The main hotspots of habitat suitability were located in the central and western parts of the study area, characterized by a more traditional model of agriculture. The distance to important foraging habitats does not influence white stork fecundity indicating that landscape composition is important when choosing the breeding site. The pairs with higher number of young were located further from other neighbouring pairs and at the areas with lower density of pairs in general. This is probably linked to the lower competition for food between more distant breeding pairs. Our results show that the traditional agricultural use in mosaics of pastures, meadows and aquatic habitats promotes white storks nesting.

Nest orientation and proximity to snow patches are important for nest site selection of a cavity breeder at high elevation

Timing and location of reproduction are central to reproductive success across taxa. Among birds, many species have evolved specific strategies to cope with environmental variability including shifts in timing of reproduction to track resource availability or selecting suitable nest location. In mountain ecosystems, complex topography and pronounced seasonality result in particularly high spatiotemporal variability of environmental conditions. Moreover, the risk of climate‐induced resource mismatches is particularly acute in mountain regions given that temperature is increasing more rapidly than in the lowlands. We investigated how a high‐elevation passerine, the white‐winged snowfinch Montifringilla nivalis, selects its nest site in relation to nest cavity characteristics, habitat composition and snow condition. We used a combination of field habitat mapping and satellite remote sensing to compare occupied nest sites with randomly selected pseudo‐absence sites. In the first half of the breeding season, snowfinches preferred nest cavities oriented towards the morning sun while they used cavities proportional to their availability later on. This preference might relate to the nest microclimate offering eco‐physiological advantages, namely thermoregulatory benefits for incubating adults and nestlings under the harsh conditions typically encountered in the alpine environment. Nest sites were consistently located in areas with greater‐than‐average snow cover at hatching date, likely mirroring the foraging preferences for tipulid larvae developing in meltwater along snowfields. Due to the particularly rapid climate shifts typical of mountain ecosystems, spatiotemporal mismatches between foraging grounds and nest sites are expected in the future. This may negatively influence demographic trajectories of the white‐winged snowfinch. The installation of well‐designed nest boxes in optimal habitat configurations could to some extent help mitigate this risk.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

Результаты мониторинга гнездовых популяций солнечного орла в Дагестане (Россия) в 2022–2023 гг.

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

О гнездовании степного орла в Дагестане

О гнездовании степного орла в Дагестане

Further dietary samples for Eastern Barn Owls Tyto javanica near Tamworth, New South Wales, revealed by habitat clearance

The diet of the Eastern Barn Owl Tyto javanica was investigated by examination of two samples of pellets (n = 11 and 39), pellet debris and prey remains from: (1) an occupied nest with fledgling in May 2009, and (2) an Owl’s winter roost in August 2009 near Tamworth in the grain belt of New South Wales. The breeding diet consisted, by number, of 91% mammals (90% rodents, including 87% House Mice Mus musculus) and 9% common farmland birds (n = 116 food items). The winter diet consisted of 99% House Mice and 1% bird (n = 188 food items). The fledgling Owl was killed when it failed to flush from its nest hollow as the tree was being felled, during approved clearing of the now Critically Endangered White Box–Yellow Box–Blakely’s Red Gum Grassy Woodland and Derived Native Grassland. Given the dependence of the Barn Owl on House Mice, and the ongoing clearing of hollow trees, we note the potential for (a) secondary poisoning of owls by rodenticides, especially during plagues of the invasive House Mouse in the grain belt, and (b) the Barn Owl’s long-term decline in abundance in New South Wales.

Мониторинг солнечного орла в национальном парке «Хвалынский» (Саратовская область, Россия)

Мониторинг солнечного орла в национальном парке «Хвалынский» (Саратовская область, Россия)

Встречи крупных хищных птиц в Новосибирской области, Россия

Встречи крупных хищных птиц в Новосибирской области, Россия

О натальной филопатрии у солнечных орлов из Поволжской популяции

Population structure across the range of the Eastern Imperial Eagle (Aquila heliaca) remains one of the controversial issues that can be resolved by data on the distribution of juveniles from different points in the range. However, the long period of puberty, the difficulty of establishing a new breeding territory in conditions of limited food resources and nesting habitats, the high mortality of juveniles and the short lifespan of tracking devices make this task very difficult. In this respect, any reliable data on the natal philopatry of the Imperial Eagle is of great interest. We have been tagging eagles in the Ulyanovsk Region since 2017. During this time, 30 juvenile Imperial Eagles were fitted with Aquila GPS/GSM trackers. During subsequent tracking of the tagged individuals, two nesting attempts were recorded. The first nesting attempt was observed with the female eagle Avralka, which was tagged as a nestling in 2017 in the Melekessky district. In the spring of 2021, Avralka stayed near the renovated nest until early May, but did not breed that season and the connection with the bird was lost after that. Avralka's nest was also located in the Melekessky district, only 12 km from her parents' nest. This breeding territory was previously unknown to us. In 2023, the male eagle Sura, tagged as a nestling in 2018 in the steppe valley of the middle reaches of the Sura River in the Karsunsky district, began nesting. On 25 May 2023 we visited its permanent site this spring and found an occupied nest with a clutch of one egg. When we visited the nest again on 14 June, we did not find a hatchling, apparently it had died in the early stages of development due to malnutrition. Sura's nesting site is located in the Dubensky district of the Republic of Mordovia, 23 km from the nesting site of its parents. Thus, in both cases, adult birds attempted to nest in the area where they were born, even though juveniles migrate quite widely during their first few years of life. This fact, despite the small sample size, suggests a rather strong natal philopatry, at least for some individuals of the Imperial Eagle, both males and females. The research was conducted as part of the “Study and Conservation of the Eastern Imperial Eagle” project carried out by the Non-Governmental Nature Conservation Centre “KAVKAZ” (NABU-Kavkaz) in cooperation with the Russian Bird Conservation Union (RBCU) and the German Nature and Biodiversity Conservation Union (NABU), with support from the NABU International Foundation and the VGP Foundation.

Breeding biology of the Egyptian Vulture, Neophron percnopterus, in the Beypazarı area, Turkey

The Egyptian Vulture Neophron percnopterus is globally endangered and its population shows a decreasing trend. Within Turkey, the largest breeding population is found in the Beypazarı region north of Ankara. In the breeding season of 2020, we identified 109 occupied nest sites and breeding activities were recorded in 90 of them (breeding propensity 82.6%). Seventy-one young fledged from 62 nests and 28 nests failed, which gives a breeding success of 0.69 successful pairs per active nest, a fledging success of 1.15 fledglings per active nest, and a productivity of 0.65 fledglings per occupied nest site. Electrocution and collision, poisoning, and habitat loss are the main threats to the species in Turkey. In our study area, the number of active nests increased from 69 in 2016 to 90 in 2020.

Habitat use and reproductive success of ospreys in central interior California

The osprey (Pandion halieatus) declined globally in the mid-late 20th century due primarily to pesticide contamination that reduced reproduction. The species has recovered through much of its range, and its range in California has increased. The species has received limited attention in recent decades, despite recommendations that it be monitored as an environmental indicator. In 2021, we located a sample of 39 osprey occupied nests near the Sacramento River and at reservoirs and small ponds in central interior California and determined habitats used and reproductive success. Nearly one-third of nests were located within 100 m of waterbodies and 88% were within 1000 m. The median distance of nests from roads was 51 m. Thirty-four (87%) of occupied nests were on anthropogenic sites, including utility poles, poles erected for ospreys, transmission towers, light poles, and port structures. Only five nests (13%) were in trees and snags. Nearly half (48%) of nests were on platforms constructed on utility poles and on poles erected for ospreys, both placed to protect electrical systems. Water levels in reservoirs, and some small farm ponds, were lower than average in 2021 due to drought, while the Sacramento River and Port were less affected. Twenty-four (71%) of 34 adequately monitored nests were successful in fledging at least one young. Productivity averaged 1.27 young/occupied nest, suggesting a healthy population. Reproductive success differed significantly among nests at different water body types, with river-port, reservoir, and pond sites exhibiting high, moderate, and low productivity, respectively. Our results document a range expansion into central interior California, presumably in response to reduced pesticide levels, reservoir creation, and availability of anthropogenic nest sites. Results also suggest that drought, and thus predicted warming and drier climate, may disproportionately affect populations nesting at non-riverine habitats by reducing the amount foraging area and increasing the distance from nest sites to foraging areas.

Developing an environmental DNA protocol for Hazel Dormouse surveys

Recording Hazel Dormouse (Muscardinus avellanarius) presence allows conservation and mitigation efforts to be effectively directed towards populated sites. As it is a protected species, licences are required for survey methods which disturb the animals or their habitat. Therefore, reliable low disturbance survey techniques are desirable. In this study, we tested the potential of detecting environmental DNA (eDNA) from soil as a survey method for dormice. Firstly, we designed species-specific primers and the associated PCR protocol using tissue samples from Hazel Dormice. To ensure specificity, we also checked the protocol against tissue samples from non-target species. Next, we collected soil samples from occupied sites in England to test the methodology with environmental samples. This included testing site-level heterogeneity of dormouse DNA distribution and localised level DNA distribution surrounding occupied nest boxes. Finally, we tested the soil for DNA presence changes over time, after removal from the site. Using eDNA for dormouse surveys is promising. Our results indicate that a usable survey methodology can be developed, providing a relatively low cost and time-efficient tool when compared to existing dormouse survey methods. Future work should aim to further understand the changes of dormouse eDNA through time. Through identifying populated sites, eDNA could support mitigation projects and help to direct dormouse conservation efforts.

Status of breeding birds at Observatorio and Goffré Islands, Argentina

Continental islands are often sites of low diversity and endemism, as well as important areas for the protection of bird populations, especially seabirds. On Isla Observatorio and the Año Nuevo Islands, in the Southwestern Atlantic, the latest assessment of avifauna dates from more than 20 years ago. In this study, we use a combination of methods to update the status of the main seabird colonies and the most abundant avian terrestrial predator at Observatorio and Goffré Islands during the breeding season. In only 4.5 km2, the islands would harbour ~ 90,000 breeding seabirds. Seabird colonies occupied different areas of the islands and varied in their population status, with Imperial Shags (Leucocarbo atriceps) showing an increase and Southern Giant Petrels (Macronectes giganteus) a decrease according to the last surveys. Magellanic Penguin (Spheniscus magellanicus) population estimations also suggest a decrease but the last survey was based on total, and not on occupied nest sites. We recorded and assessed one new breeding species: The globally near-threatened Striated Caracara (Phalcoboenus australis), which has an important breeding population of around 15 territorial pairs at Observatorio Island. These islands appear to be an important regional bird site and future studies would determine their trends and threats, especially those related with invasive species.

Who stole my nest? Weaver nests used as nest lining

Birds stealing nest material from a neighbour’s nest is well known, but stealing entire nests is less well known. This has been reported nine times for raptors and waterbirds taking the domed nests of weaverbirds. Three waterbird species and five raptor species are involved. Nests of four weaver species were identified. Three records were from Kwa-Zulu Natal in South Africa, and the rest from elsewhere in Africa. Weaver nests included green nests, but most were old nests, and at least one occupied nest (with eggs). Since green nests were not the norm, the weaver nests were probably taken as a source of plant material, rather than for any specific benefit relating to weaver nests.

Rotenone Use and Subsequent Prey Loss Lowers Osprey Fledging Rates Via Brood Reduction

ABSTRACT Fisheries managers used the fish toxicant rotenone to eradicate an undesirable brown bullhead (Ameiurus nebulosus) population and all other fish species at Hyatt Reservoir, Oregon, on 12 October 1989. This 4-yr study (1988–1990, 1992) compared effects of that rotenone project on Ospreys (Pandion haliaetus) nesting at Hyatt Reservoir and nearby Howard Prairie Reservoir (untreated reference)—the latter a reservoir where both brown bullheads and hatchery-released rainbow trout (Oncorhynchus mykiss) prospered. Because Hyatt Reservoir was treated after Osprey fall migration in 1989, the first 2 yr (1988 and 1989) yielded pretreatment information: number of Osprey pairs was unchanged and reproductive rates were similar and consistent at the two reservoirs. Yearling fish (200–250 mm) were restocked at Hyatt Reservoir in the spring of 1990 and Ospreys returned each year following rotenone treatment, with no decline in the number of occupied or active nests. The negative effect of the rotenone treatment on Ospreys was short-term, resulting in reduced reproductive rates (young/occupied nest, young/active nest, and young/successful nest) during the first nesting season posttreatment, although hatching rates were not affected. Osprey dive success and prey delivery rates declined sharply in 1990, leading to competition for food among siblings and brood reduction. Osprey reproductive rates and prey delivery rates at Hyatt Reservoir in both 1990 and 1992 remained below the extremely high pretreatment rates, but within the range required for population stability. Serious adverse effects of the fish loss on Osprey reproduction were minimized by: (1) the delay of the rotenone application until after breeding season, (2) the restocking of the treated reservoir in the following spring with some larger (yearling) fish (though the timing was late), (3) the maintenance of a supplemental feeding program for a nesting pair of Bald Eagles (Haliaeetus leucocephalus), which minimized kleptoparasitism on Ospreys, and perhaps most important (4) the presence of nearby water bodies, where Osprey obtained some fish in the 1990 and 1992 breeding seasons.