The breeding performance of raptors in urban landscapes: a review and meta-analysis

Global urbanisation is rapidly increasing and can have profound impacts on wild flora and fauna. For many species, the impacts are detrimental and irreversible, whereas others are able to colonise and apparently thrive in these novel, human-made environments. Raptors are particularly susceptible to changes in the environment due to their position at the end of the food chain, yet some species are increasingly associated with towns and cities. To explore the impact of urbanisation on raptors, we reviewed the literature and compared breeding performance in urban and rural populations globally. In general, raptors began breeding earlier and had larger brood sizes in urban compared to rural environments. However, some of these raptors also fledged fewer young in urban habitats, apparently caused largely by a lack of prey and, in some cases, increased human disturbance. As such, urban environments may act as ecological traps for some raptor species. Species differed in their response to urbanisation. In particular, specialist bird predators such as Peregrine Falcons (Falco peregrinus) had a higher breeding performance (clutch size, brood size, number to fledge and nest success) and showed a positive response to urbanisation compared to those that predate on small mammals, such as Eurasian Kestrels (F. tinnunculus), which showed a negative response. This suggests that prey availability is one of the most important determinants of the success of urban-nest- ing raptors. We demonstrate a need for continued research into the breeding performance of raptors that live in urban environments, and stress the importance of focusing on the reasons for any differences in breeding performance between urban and non-urban environments in order to aid conservation and management efforts for this iconic bird grou

Breeding performance of an apex predator, the peregrine falcon, across urban and rural landscapes

Urban environments present wildlife with major challenges and yet surprising numbers of species have colonised towns and cities globally. Despite the growing realisation that urban centres can be important habitats for wildlife, why some species do better than others in urban environments remains poorly understood. Here, we compare the breeding performance of an apex predator, the peregrine falcon (Falco peregrinus), in urban and rural environments, and test whether variation in reproductive success between and within environments is driven by prey. Historical breeding data were collected from raptor study groups across Great Britain between 2006 and 2016, from 22 urban and 58 rural nest sites, involving 101 and 326 nesting attempts, respectively. Prey density, biomass and diversity around the individual nests was estimated using modelled estimates from a national bird census. Urban peregrines produced more fledglings and had a higher overall nesting success (i.e. whether a nesting attempt was successful or unsuccessful) than rural peregrines. Prey density and biomass were significantly higher, and diversity significantly lower, in the urban sites, and explained the variation in reproductive success within both the urban and rural environments. Therefore, urban environments in Great Britain appear to provide peregrine falcons with superior habitats in terms of prey availability compared to rural habitats. We conclude that some apex predators can benefit from urban environments and that urban planning has the potential to benefit biodiversity across many trophic levels

Several parameters that influence body size in the sea anemone Actinia equina in rock pools on the Yorkshire coast

Despite being classed as an asocial species, aggregations of sea anemones can be common in abundant species. UK populations of the geographically common aggressive intertidal sea anemone Actinia equina, form clustered aggregations notwithstanding a violent nature towards neighbours and relatives. Smaller in body size, and more abundant than those found in warmer climates, little research has been undertaken to discover what factors affect body size. This study investigates whether aggregation, distance to neighbour, submergence at low tide or pH in rock pools affect body size of A. equina in their natural habitat. Populations were investigated at five sites on the Yorkshire coast during August and September 2016. A total of 562 anemones were recorded revealing that solitary anemones were significantly larger than those found in clustered aggregations. In addition, anemones found submerged in rock pools at low tide were significantly larger than those found on emergent rock, and smaller anemones were found in significantly higher pH conditions (8.5+) than larger anemones. Anemones submerged at low tide are constantly able to feed and not subject to harsh conditions such as wind exposure and temperature, hence they can achieve larger sizes. Consequently, the size of the anemones may reflect a trade-off between the benefits of aggregating in exposed environments and the costs of competition for a reduced food resource

Raptors, racing pigeons and perceptions of attacks

Raptors are often the cause of human-wildlife conflict because they may predate economically valuable species, and it is the perceived extent of predation that may augment conflict between raptors and people who keep and race pigeons. This study uses data obtained through questionnaires and an online raptor-attack reporting feature to investigate the frequency of racing pigeon losses and the perceptions of pigeon fanciers. Responses suggest that those who kept more pigeons and entered more races lost a higher proportion of pigeons. Losses were also influenced by the predatory species: sparrowhawks (Accipter nisus) were more likely to attack pigeons at lofts, whilst peregrines (Falco peregrinus) were more likely to attack pigeons during training, with patterns linked to the raptors' breeding seasons. Pigeon fanciers were almost unanimous in their perception that raptors threaten the future of the hobby. Previous studies show that only a small proportion of racing pigeons are likely to be lost to raptors, yet pigeon fanciers believe that raptors are the main cause of losses, highlighting a possible mismatch between the perceived and actual causes of loss. This misconception may be a main source of this human-raptor conflict, so educating pigeon fanciers about the true impact of raptors could help to alleviate the issue. A shift in the beginning of the pigeon racing season by one month, and careful sighting of pigeon lofts in gardens, are also recommended in order to reduce raptor attacks

Ghost crab burrow density at Watamu Marine National Park: an indicator of the impact of urbanisation and associated disturbance?

Ghost crab (Ocypode species) burrow densities have previously been used as an indicator of anthropogenic impact. This study aimed to assess the burrow density of Ocypode species (O. ryderi and O. cordimanus) at four sites across Watamu Marine National Park, Kenya. Two sites were in front of hotel complexes (denoting a high degree of urbanisation), and two were in front of residential housing among coastal scrub (denoting a low degree of urbanisation). The findings reveal significantly higher burrow densities at sites in front of residential housing, which was the less developed area. This provides further evidence that Ocypode burrow densities can be used, where other methods would be impractical, to estimate the impact of some human activities along beach fronts, such as at Watamu Marine National Park

Plastic ingestion in adult and fledgling Manx Shearwaters Puffinus puffinus on Skomer Island, Wales

Plastic debris is ubiquitous in the marine environment, and seabirds are among the most impacted marine vertebrates. Plastic ingestion was investigated in an internationally-important breeding population of Manx Shearwaters Puffinus puffinus on Skomer Island, Wales in 2018–19. Opportunistic necropsies were carried out on a total of 34 birds to collect contents of the gastrointestinal tract: 13 adults in April – July 2018 and 12 fledglings during September 2019, and a further nine opportunistic necropsies carried out from adults in July – September 2018. The presence, quantity, size and colour of plastic in the gastrointestinal tract was investigated. Plastic was found in 71% of stomach contents (68% of adults, 75% of fledglings). Adults were found to have larger plastic pieces in their gastrointestinal tract than fledglings, and lighter birds had larger pieces of plastic in their tracts than heavier birds. This study shows that Manx Shearwaters on Skomer Island are vulnerable to plastic ingestion, and that adults are likely to pass plastic to their chicks

The impact of human disturbance on temporal partitioning within carnivore communities

1. Interspecific competition is an important evolutionary force, influencing interactions between species and shaping the composition of communities. In mammalian carnivores, to reduce the risks of negative encounters between competitors, species can employ a strategy of temporal partitioning, adapting activity patterns to limit synchronous activity. This strategy of non-human competitor avoidance, however, may be influenced by the expansion of human activities, which has driven wildlife towards nocturnality. 2. Therefore, it could be hypothesised that the disruption of temporal niche partitioning by humans and their activities could increase temporal overlap between carnivores, enhancing interspecific competition. 3. We reviewed the published literature systematically, and employed generalized linear models to quantitatively evaluate the relative influence of a range of human, meteorological and ecological variables on the coefficients of temporal overlap within carnivore communities on a global scale. 4. None of the models investigated showed evidence of an impact of humans on temporal partitioning between carnivores on a global scale. This illustrates that temporal avoidance of humans and competitors does not always follow a consistent pattern, and that its strength may be context-dependent and relative to other dimensions of niche partitioning (spatial and trophic). 5. Similarly, the regulation of activity patterns may be under strong site-specificity, and be influenced by a combination of biotic and abiotic characteristics. Temporal avoidance of both humans and competitors may be regulated by short, reactive responses that do not impact activity patterns in the longer term. 6. Although we did not detect a global disruption of temporal partitioning due to human disturbance, carnivore communities may still experience an increase in interspecific competition in other niche dimensions. Further research would benefit from using controlled experimental designs and investigating multiple dimensions of niche partitioning simultaneously. Finally, we recommend complementing the coefficient of temporal overlap with other metrics of fine-scale spatiotemporal interactions

Risk factors for severe and fatal heat-related illness in UK dogs—a VetCompass study

Heat-related illness (HRI) is predicted to increase in dogs due to rising global temperatures. This study evaluated retrospective VetCompass veterinary clinical records to explore geographical variability and ambient conditions associated with HRI events in UK dogs, and report the intrinsic (canine) and extrinsic (location, trigger, ambient weather) risk factors for severe disease and fatal outcome in dogs affected by HRI. Dogs living in London had the greatest odds for developing HRI compared with dogs living in the North West (OR 1.9, 95% CI 1.31–2.74). The median ambient temperature on days of HRI events was 16.9 °C. For dogs with HRI, age, bodyweight and trigger were risk factors associated with severe disease. Age, skull shape and clinical grade of HRI presentation were associated with a fatal outcome. Whilst the majority of HRI events overall were triggered by exertion, the risk of severe disease was greater in situations where dogs could not escape the heat source (vehicular confinement), and the risk of death in HRI cases was greater for those dogs with reduced capacity to thermoregulate (older and brachycephalic dogs). These results highlight the need for better owner awareness of the factors that increase the risk of severe and fatal HRI, as a first stage in protecting canine welfare in the face of rising global temperatures

Evidence of the Trade-Off between Starvation and Predation Risks in Ducks

The theory of trade-off between starvation and predation risks predicts a decrease in body mass in order to improve flight performance when facing high predation risk. To date, this trade-off has mainly been validated in passerines, birds that store limited body reserves for short-term use. In the largest avian species in which the trade-off has been investigated (the mallard, Anas platyrhynchos), the slope of the relationship between mass and flight performance was steeper in proportion to lean body mass than in passerines. In order to verify whether the same case can be applied to other birds with large body reserves, we analyzed the response to this trade-off in two other duck species, the common teal (Anas crecca) and the tufted duck (Aythya fuligula). Predation risk was simulated by disturbing birds. Ducks within disturbed groups were compared to non-disturbed control birds. In disturbed groups, both species showed a much greater decrease in food intake and body mass during the period of simulated high risk than those observed in the control group. This loss of body mass allows reaching a more favourable wing loading and increases power for flight, hence enhancing flight performances and reducing predation risk. Moreover, body mass loss and power margin gain in both species were higher than in passerines, as observed in mallards. Our results suggest that the starvation-predation risk trade-off is one of the major life history traits underlying body mass adjustments, and these findings can be generalized to all birds facing predation. Additionally, the response magnitude seems to be influenced by the strategy of body reserve management