Malar stripe size and prominence in peregrine falcons vary positively with solar radiation: support for the solar glare hypothesis

Many falcons ( Falco spp.) exhibit a distinct dark plumage patch below the eye, termed the malar stripe. This stripe is hypothesized to reduce the amount of solar glare reflected into the eyes while foraging, thereby increasing hunting efficiency in bright conditions. Here, we use a novel, global-scale correlative approach to test this ‘solar glare hypothesis' in peregrine falcons ( Falco peregrinus ), the most widespread falcon species, using web-sourced photographs from across the species' global range. We found that the size and prominence of the malar stripe were positively associated with average annual solar radiation, but not with other environmental variables, such as temperature and rainfall. Our results provide the first published evidence for the hypothesis that this plumage feature functions to reduce the amount of solar glare reflected into the falcon's eyes, thereby improving the ability to pinpoint and target agile prey in bright conditions.

The use of point-of-view cameras (Kittycams) to quantify predation by colony cats (Felis catus) on wildlife

Context Domestic cats (Felis catus) are efficient and abundant non-native predators, recently labelled as primary contributors to global biodiversity loss. Aims Specific research goals included determining the proportion of hunters, estimating hunting efficiency, identifying primary prey and examining predictors of kill rate and efficacy. Methods We investigated hunting of wildlife by stray cats living in managed outdoor colonies on a barrier island in the southeastern USA, and monitored 29 stray cats seasonally in 2014 and 2015 using Kittycam video cameras. Key results In total, 24 cats exhibited hunting behaviour and 18 captured prey. The estimated average daily predation rate from these successful hunters was 6.15 kills per 24-h period. Hunting effectiveness (percentage of capture attempts that translate to a kill) was an average of 44%. The most common type of prey captured was invertebrate (primarily Orthopteran and Hemipteran insects), followed by amphibians and reptiles. Eighty-three percent of kills occurred between dusk and dawn. Conclusions Colony location (near undeveloped island habitat) was related to higher kill rates. Cat sex and nocturnal hunting activity were related to greater hunting efficiency. Implications These results address the significant gap in knowledge about stray cat hunting activities, and raise conservation concerns for some groups of organisms (reptiles and amphibians) that have not been widely identified as vulnerable to cat predation.

Hunting efficiency of Red-footed Falcons in different habitats

We studied hunting success of 13 male Red-footed Falcons by radio-telemetry in the second phase of chick rearing. We coded 484 hunting events, and the success measured in captured prey biomass/minute was exceedingly high in corn fields. This is mainly caused by the fact that the effectiveness of hunting for vertebrate prey was high on the harvested stubble fields. Moreover the observed falcons hunted for insects in these stubble field and alfalfa fields most successfully. In the studied habitat the chick feeding period of Red-footed Falcons coincide with the harvest of cereal fields, and the suddenly created lower vegetation cover increases temporarily the accessibility of prey items. Till they were available and could be efficiently harvested, the falcons hunted on the fields within a 1 km radius from the nesting colony for the more profitable vertebrate prey. Thereafter they searched for vertebrate prey on the fields located at average 1–2.5 km distance from the colony. In the later zone falcons started to hunt insects, too, but approximately third of the captured insects (36.4%) was consumed immediately and was not delivered to the colony. Conversely larger prey was almost always (98.1%) carried directly to the nest site. Only one part of the Field Voles was observed to be eaten regularly: the brain. Finally later in the breeding season falcons were observed more and more often to hunt in the nearest fields again, this time for insects. Probably due to the depletion of the distant plots, the closer fields with lower investment became a competitive alternative for the birds. Our results highlight the fact that even for such characteristic short-grass specialist birds as Red-footed Falcons the prey sources offered by arable lands might be temporarily exploited with success. Hence it is very important to integrate the measures offered by agri-environment schemes into the management of this threatened species.

Learning to hunt: the role of experience in predator success

Animal behaviour is a composite of innate and learned components. During their lifetimes, animals typically gain experience and manifest learning, thereby augmenting or modifying genetically determined, innate behaviour patterns. Following a training period during which predatory fish (jade perch, Scortum barcoo) were allocated to treatments and given experience of either live prey (mosquitofish, Gambusia holbrooki), freshly killed prey, or cichlid pellets with equal nutritional value, we tested the response of the predators to the prey in an experimental arena. Across all treatments, there was no difference in the number of attacks made by the predators on the prey, however the predators with experience of live fish prey were significantly more successful in capturing prey than those without previous experience of live prey. These results suggest that, in this piscivorous predator, the recognition of prey has an innate component, but that hunting efficiency is increased through experience. These findings are discussed in terms of their implications for the release of hatchery-reared fish into the wild, the majority of which are predatory.