Nest boxes buffer the effects of climate on breeding performance in an African urban raptor

Abstract

As the world's human population increases, transformation of natural landscapes into urban habitats continues to increase. In Africa, rates of human population growth and urbanisation are among the highest in the world, but the impacts of these processes on the continent's biodiversity remain largely unexplored. Furthermore, the effects of ongoing anthropogenic climate change are likely to be severe and to interact with urbanisation. Some organisms appear resilient to urbanisation, and even proliferate in human-modified environments. One such species is the peregrine falcon Falco peregrinus in Cape Town, South Africa. Using a long-term data set (1989-2014), we investigate the relationship between breeding attempts, timing of breeding and breeding performance under varying weather conditions. Exploring these issues along an urbanisation gradient, we focus on the role of artificially provided nest boxes, and their capacity to buffer against extreme weather events. Pairs in more urbanised areas, and particularly those in nest boxes, were more likely to breed and to commence breeding earlier. Additionally, pairs using nest boxes were more likely to breed in years with higher rainfall. Warm and dry weather conditions generally advanced the timing of breeding, although this relationship with weather was not seen for urban pairs using nest boxes. Furthermore, weather did not impact breeding performance directly (breeding success and fledged brood size), but timing of breeding did, with earlier breeders producing more fledglings. Our study shows that falcons breeding in specially provided nest boxes were less sensitive to local weather dynamics than pairs using more natural nest sites. This has important implications as it suggests that the managed provision of such nesting sites can help this key urban species to cope with extreme weather events, which are predicted to increase with climate change.

Nest-type associated microclimatic conditions as potential drivers of ectoparasite infestations in African penguin nests

“…Fleas and ticks are obligate haematophagous and high host infestations can affect the condition and health of the host (Lehmann 1993). Although ticks and fleas are known vectors of some haemoparasites (Sonenshine 1993;Bitam et al 2010), we did not observe a higher incidence of haemoparasites in the penguins that occupied artificial nests. However, it is recommended that this result be confirmed using molecular techniques as it is possible that the microscopic method that we used is not sensitive enough (Campbell and Ellis 2007).…”

“…The higher parasite infestations in artificial nests are most probably the result of more favourable microclimatic conditions. Fleas and soft ticks are nidicolous ectoparasites that spend most of their life cycle in the nest of their host (Jordan 1942;Sonenshine 1993). As mentioned before, fleas and ticks are ectothermic and as a result their development and survival is influenced by temperature and humidity in the nest.…”

“…ectoparasites that live in or near to the host dwelling in for example, cracks, under stones and among the nest material (Sonenshine 1993;López-Rull and Macías Garcia 2015). Although all the life stages of fleas (egg, larva, pupa and adult) occur in the nest, only the adults consume blood, while most or all of the tick life stage (egg, larval, nymph and adult), depending on the species, require a blood meal (Sonenshine 1993;Bitam et al 2010). Fleas and ticks, being arthropods, are ectothermic and thus sensitive to the microclimatic conditions in the nest (López-Rull and Macías Garcia 2015).…”

“…High ectoparasite infestations can induce adult birds to abandon eggs and chicks, such as seen in Peruvian seabirds deserting their nests in colonies highly infested with ticks (Ornithodoros amblus) (Duffy 1983). Ectoparasites, and especially ticks, and fleas also act as vectors for pathogens such as rickettsia, protozoa and viruses (Sonenshine 1993;López-Rull and Macías Garcia 2015) that can affect the health of the bird (Heylen et al 2015). High ectoparasite infestations in the nests can therefore affect the population size and survival of endangered bird species (Williams et al 2013).…”

The Biological Deserts Fallacy: Cities in Their Landscapes Contribute More than We Think to Regional Biodiversity

“…Altered conditions in cities can lead to changes in trophic interactions that can free up resources and increase prey density. For example, higher prey density and reduced threat of persecution in cities has been linked to success in several urban raptors, including Cooper's hawks ( Accipiter cooperii ), peregrine falcons, crested goshawks ( Accipiter trivirgatus ), and Mississippi kites ( Ictinia mississippiensis ; Parker 1996 , Cava et al 2012 , Millsap et al 2013 , Kettel et al 2018 , 2019 , Sumasgutner et al 2020 ). However, abundance does not necessarily correspond to higher reproductive success, and raptors with the greatest reproductive performance in urban compared with rural landscapes consume birds instead of mammals, which are often scarce and nocturnal in urban environments (Kettel et al 2019 ).…”