To get sick or not to get sick—Trichomonas infections in two Accipiter species from Germany

Trichomonosis caused by the flagellate Trichomonas gallinae is one of the most important avian diseases worldwide. The parasite is localised in the oesophageal area of its host and mainly infects pigeon and dove species. During the last decade, a host expansion to passerine birds occurred, making the disease a potential threat for passerine predators as naïve host species. Here, we investigated the effect of the parasite on two Accipiter species in Germany which show a comparable lifestyle but differ in prey choice, the Northern goshawk (Accipiter gentilis) mainly hunting pigeons and the Eurasian sparrowhawk (Accipiter nisus) mainly feeding on passerines. We genetically identified the parasite strains using the Fe-Hydrogenase gene as marker locus and compared the incidence of parasite presence and clinical signs of trichomonosis between nestlings of the two Accipiter species. In total, we identified 14 strains, with nine strains unknown so far. There was a higher strain diversity and prevalence of Trichomonas spp. in goshawks than sparrowhawks (42.4% vs. 21.2%) whereas sparrowhawks when being infected more often displayed clinical signs of trichomonosis than goshawks (37.1% vs. 6.1%). Even though sparrowhawks were mainly infected with the finch epidemic strain and genetic data indicated some variation between isolates, no correlation with virulence could be detected. All in all, goshawks seem to be better adapted to Trichomonas infections, whereas to sparrowhawks, this is a novel disease with more severe manifestations, from individual morbidity to a higher risk of population decline caused by trichomonosis

How much to carry? Implications of maximum load carrying capacity for prey use of urban and rural Northern Goshawks <i>Accipiter gentilis</i>

Compared to their rural counterparts, urban Northern Goshawks Accipiter gentilis potentially maximize their energy delivery to the nest by exploiting heavier prey species close to their maximum carrying capacity. We aimed to assess prey use of a raptor species with distinct reversed sexual size dimorphism from a perspective of physical limitations during foraging and the transportation of prey. We estimated the theoretical maximum load carrying capacity (MLCC) of fully developed Northern Goshawks based on their flight muscle mass. Additionally, we collected data on the breeding season diet of Northern Goshawks in urban and rural habitats in Germany. By linking MLCC estimates to the diet we explained the relevance of prey size from a viewpoint of load carrying capacity. Estimates for the mean (± sd) additional portable loads were 684âg (± 237) for males and 971âg (± 235) for females, accounting for 96% and 84% of their body mass, respectively. Overall prey weight averaged higher for urban areas compared to rural ones, while the majority of prey items were between 200 and 500âg and below the estimated MLCC of both sexes, with the exception of single heavy species. Results suggest that prey use of Northern Goshawks during the breeding season is barely limited by prey transportability, since both sexes are physically capable of carrying the majority of prey species to their nest. Urban Northern Goshawks can exploit heavier, available prey species compared to their rural counterparts, allowing them to hunt larger prey closer to their MLCC. Ultimately, by maximizing their energy delivery to the nest, this presumably constitutes one key factor why Goshawks successfully colonized European cities. This study is the first to link estimates of physical limitations in prey transportation for a free-living raptor species to its prey composition in the light of colonizing urban environments

Phantom of the forest or successful citizen? Analysing how Northern Goshawks (Accipiter gentilis) cope with the urban environment

M.M. was part of the Graduate School IMPact-Vector funded by the Senate Competition Committee grant (SAW-2014-SGN-3) of the Leibniz Association. M.M. is also an associated doctoral student of the GRK2046 from the German Research Foundation (DFG). We are grateful for additional funding (Jagdabgabe) from the ‘Stiftung Naturschutz Berlin' (J0056 & J0088), the ‘Ministerium für ländliche Entwicklung, Umwelt und Landwirtschaft des Landes Brandenburg' (35-21340/7+5-51/16), the ‘Behörde für Wirtschaft, Verkehr und Innovation der freien Hansestadt Hamburg' (title: ‘Gesundheitsstatus und Ausbreitungsverhalten von Habichtnestlingen in Hamburg') and the ‘Ministerium für Energiewende, Landwirtschaft, Umwelt und ländliche Räume des Landes Schleswig-Holstein’ (V 542–42902/2016).By 2040, roughly two-thirds of humanity are expected to live in urban areas. As cities expand, humans irreversibly transform natural ecosystems, creating both opportunities and challenges for wildlife. Here, we investigate how the Northern Goshawk (Accipiter gentilis) is adjusting to urban environments. We measured a variety of behavioural and ecological parameters in three urban and four rural study sites. City life appeared related to all parameters we measured. Urban female goshawks were overall 21.7 (CI95.13-130) times more likely to defend their nestlings from humans than rural females. Urban goshawks were 3.64 (CI95.05-6.66) times more likely to feed on pigeons and had diets exhibiting lower overall species richness and diversity. Urban females laid eggs 12.5 (CI95.12-17.4) days earlier than rural individuals and were 2.22 (CI95.984-4.73) times more likely to produce a brood of more than three nestlings. Nonetheless, urban goshawks suffered more from infections with the parasite Trichomonas gallinae, which was the second most common cause of mortality (14.6, after collisions with windows (33.1. In conclusion, although city life is associated with significant risks, goshawks appear to thrive in some urban environments, most likely as a result of high local availability of profitable pigeon prey. We conclude that the Northern Goshawk can be classified as an urban exploiter in parts of its distribution.Publisher PDFPeer reviewe