Accounting for predator species identity reveals variable relationships between nest predation rate and habitat in a temperate forest songbird.

Nest predation is the primary cause of nest failure in most ground-nesting bird species. Investigations of relationships between nest predation rate and habitat usually pool different predator species. However, such relationships likely depend on the specific predator involved, partly because habitat requirements vary among predator species. Pooling may therefore impair our ability to identify conservation-relevant relationships between nest predation rate and habitat. We investigated predator-specific nest predation rates in the forest-dependent, ground-nesting wood warbler Phylloscopus sibilatrix in relation to forest area and forest edge complexity at two spatial scales and to the composition of the adjacent habitat matrix. We used camera traps at 559 nests to identify nest predators in five study regions across Europe. When analyzing predation data pooled across predator species, nest predation rate was positively related to forest area at the local scale (1000 m around nest), and higher where proportion of grassland in the adjacent habitat matrix was high but arable land low. Analyses by each predator species revealed variable relationships between nest predation rates and habitat. At the local scale, nest predation by most predators was higher where forest area was large. At the landscape scale (10,000 m around nest), nest predation by buzzards Buteo buteo was high where forest area was small. Predation by pine martens Martes martes was high where edge complexity at the landscape scale was high. Predation by badgers Meles meles was high where the matrix had much grassland but little arable land. Our results suggest that relationships between nest predation rates and habitat can depend on the predator species involved and may differ from analyses disregarding predator identity. Predator-specific nest predation rates, and their relationships to habitat at different spatial scales, should be considered when assessing the impact of habitat change on avian nesting success

Reproductive success of the wood warbler Phylloscopus sibilatrix varies across Europe

Differences in population trends across a species’ breeding range are ultimately linked to variation in demographic rates. In small songbirds, demographic rates related to fecundity typically have strong effects on population trends. Populations of a forest songbird, the wood warbler Phylloscopus sibilatrix, have been declining in many but not all regions of the European breeding range. We investigated if clutch size, hatching rate, nest survival and number of fledglings vary across Europe, and if nest survival is related to differences in the regionally dominant nest predator class (birds versus mammals). From 2009 to 2020, we monitored 1896 nests and used cameras at a subsample of 645 nests in six study regions: the United Kingdom (mid-Wales, Dartmoor, the New Forest), Germany (Hessen), Switzerland (Jura mountains) and Poland (Białowieża National Park). Number of fledglings was lowest in the New Forest (1.43 ± CI 0.23), intermediate in Jura (2.41 ± 0.31) and Białowieża (2.26 ± 0.24) and highest in mid-Wales (3.02 ± 0.48) and Dartmoor (2.92 ± 0.32). The reason for low reproductive success in the New Forest, Jura and Białowieża was low nest survival, and large clutch sizes in Białowieża did not compensate for high nest losses. High reproductive success in mid-Wales and Dartmoor was due to high nest survival and large clutch sizes. Overall predation rates were similar everywhere despite variation between the regions in the dominant nest predator class. Unsuccessful nests in mid-Wales were mainly predated by birds; in Dartmoor, the New Forest, Hessen and Jura similarly by birds and mammals; and in Białowieża exclusively by mammals. Regional reproductive success does not match the population trends recently reported for the wood warbler in the six study regions (i.e. high reproduction ≠ positive trend). Annual survival may be a decisive factor, but it is difficult to quantify for a nomadic species such as the wood warbler that rarely returns to the same breeding locations

Competition or co-existence of reintroduced, critically endangered Mauritius fodies and invasive Madagascar fodies in lowland Mauritius?

Habitat destruction and introductions of invasive species have been primary causes of endemic species loss on oceanic islands. This paper addresses the question of whether a reintroduced population of a critically endangered island endemic, the Mauritius fody (Foudia rubra) is competing or co-existing with an exotic congener, the Madagascar fody (F. madagascariensis). We investigated habitat use and feeding ecology of the Mauritius fody during two early phases of its reintroduction onto a restored islet, and compared these parameters with the sympatric population of Madagascar fodies. The number of Mauritius fody territories increased from 4 to 20 in a seven month period following release, and overall mean territory area (c. 1 ha) was significantly larger than that of the more abundant Madagascar fody (c. 0.07 ha). The initial four territories were located in mature coastal forest, whilst those of the Madagascar fody were characterised by open canopy, smaller trees and grass-dominated ground cover. Mauritius fodies foraged mainly in dead leaves for insects, whilst the Madagascar fody fed primarily on the seeds of a native grass species. Mauritius fody territories later expanded to include a range of habitats. Differing ecological requirements indicate that divergence between these congeners may be sufficient for them to coexist and exploit contrasting resources on restored islets. We discuss the implications of these findings for both the long-term restoration of the Mauritius fody and other avian recovery programmes and highlight the critical importance of long-term post-release monitoring to assess the success of reintroduction to offshore islets as a long-term conservation strategy

Captive breeding and rearing of critically endangered Mauritius fodies Foudia rubra for reintroduction

In-situ captive rearing of endangered passerines for reintroduction has rarely been used as a conservation tool. Nests of Mauritius fodies threatened with predation by introduced mammalian predators were harvested from the wild, and chicks were reared to independence for release onto an offshore, predator-free island. The daily probability of the survival was higher in captivity than in the wild, and 69 chicks were reared to fledging of which 47 would have been expected to fledge in the wild. Harvesting of nests probably had little impact on the wild population. Captive breeding trials on Mauritius fodies showed that large numbers of individuals could be produced for a release program from a small number of pairs if enough space was provided. Artificial incubation of passerine eggs and rearing of chicks can be used to increase the productivity of endangered taxa. Zoos can play an important role in in-situ conservation programs through provision of avicultural expertise and training of local staff