Cunningham et al. (2015) Can behaviour buffer the impacts of climate change on an arid-zone bird? Ostrich 86: 119-126
Behavioural thermoregulation, particularly the use of cool microclimates, is one method by which organisms could avoid the worst effects of climate warming. However, retreat into cool microsites, e.g. shady vegetation or burrows, may carry important lost-opportunity costs. These could include reduced opportunity for foraging, breeding or territorial defence, each carrying implications for fitness. We investigated patterns of microclimate use and foraging behaviour by Southern Fiscals Lanius collaris in the Kalahari. We used Ivlev's electivity index to assess preference of breeding males for perch types with different thermal properties. We found that Southern Fiscals preferred to hunt from high, sunny perches at all times, except on hot afternoons (air temperature >35 °C), when they switched their preference to high, shaded perches. Black-bulb thermometers indicated shaded perches were always cooler than sunny perches, especially on hot afternoons. Therefore, Southern Fiscals could reduce thermoregulatory costs by switching foraging locations. However, Southern Fiscal foraging success rates were highest when hunting from sunny perches, and were reduced by c. 50% when hunting from shaded perches. Our data suggest that Southern Fiscals were making a trade-off on hot afternoons, compromising foraging intake in return for thermal benefits. We discuss potential costs and consequences of this trade-off under climate change. http://www.tandfonline.com/doi/abs/10.2989/00306525.2015.1016469
Westrip & Bell (2015) Breaking down the species boundaries: selective pressures behind interspecific communication in vertebrates. Ethology DOI: 10.1111/eth.12379
Studying heterospecific communication provides an opportunity to examine the dynamics of cross-species social behaviour. It allows us to ask questions about the extent to which the transfer of information is adaptive or accidental and provides an empirically tractable context for manipulating relationships. To date, most studies of heterospecific communication have focussed on receivers. However, the selective pressures on signallers can be as important in determining the dynamics of interspecific communication. Here, we propose a simple framework for thinking about cross-species information transfer, which (i) considers whether information exchange is either accidental or adaptive and (ii) whether it is unidirectional or bidirectional. To clearly classify interactions, it is necessary to quantify all of the payoffs of interspecific communication to both signallers and receivers. This requires accurate characterisation of the currency influenced by cross-species communication (e.g. weight gain, foraging success, survival). However, quantifying the payoffs may be difficult, because each side may be benefiting via different currencies. To date, studies on heterospecific communication have focussed on only one dimension of a niche (usually antipredator or foraging signals). However, because niches are multidimensional, investigations should incorporate multiple aspects of a species’ niche, to get a better perspective on why we see certain patterns of information use between species.
Flower et al. (2015) Dual parasitism of fork-tailed drongos by African and Jacobin cuckoos. Ostrich 86: 1-2
Different species of brood parasitic birds, which lay their eggs in the nests of host foster-parents, rarely target the same host species population. We report brood parasitism of Fork-tailed Drongos Dicrurus adsimilis in the southern Kalahari Desert by both African Cuckoo Cuculus gularis and Jacobin Cuckoo Clamator jacobinus serratus. Drongos are the only known host for the African Cuckoo, and were more frequently parasitised by this species (21.8% nests). Nevertheless, parasitism rates suggest that in the Kalahari, drongos are also an important host for Jacobin Cuckoo (4.6% nests). Jacobin Cuckoos likely compete with African Cuckoos for drongo hosts, as exemplified by the occurrence of both African and Jacobin Cuckoo eggs in the same drongo clutch. The drongo's defensive adaptations to parasitism by African Cuckoos, including egg rejection, may also curtail parasitism by Jacobin Cuckoos. The extent of competition between these cuckoo species and whether they possess adaptations to prevent one another's access to drongo hosts remains to be explored.