Hart Lorinda A, Downs Colleen T, Brown Mark
School of Life Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
School of Life Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville, Pietermaritzburg 3209, South Africa.
J Therm Biol. 2017 Feb;64:19-25. doi: 10.1016/j.jtherbio.2016.12.003. Epub 2016 Dec 16.
The thermoregulatory capacity of a species can determine which climatic niche it occupies. Its development in avian chicks is influenced by numerous factors. Furthermore, it is suggested that altricial chicks develop their thermoregulatory capacity post-hatching, while precocial chicks develop aspects of this in the egg. We investigated the development of thermoregulation of four co-occurring seabird species in the Seychelles; namely white, ground-nesting white-tailed tropicbirds (Phaethon lepturus) and tree-nesting fairy terns (Gygis alba); and dark plumaged, tree-nesting lesser noddies (Anous tenuirostris) and ground- and tree-nesting brown noddies (A. stolidus). White-tailed tropicbirds have semi-altricial chicks, while the remaining species have semi-precocial chicks. Cloacal temperatures (T) were measured at five day intervals from newly hatched chicks and compared over time, and with adult Ts. Initial Ts of all chicks, except fairy terns, were lower than those taken when chicks were older. Brooding cessation generally coincided with feather development, as did an increase in T Mean chick T was significantly lower than mean adult T for all species, but only white-tailed tropicbird and brown noddy chicks in tree nests differed significantly from mean adult T when chick T at five day intervals were considered. There was a significant interactive effect of nest site and age on brown noddy chick T but chick colour did not have a significant effect on T. However, brown noddy chicks on dune crests maintained a constant T sooner than chicks in tree nests. Our results demonstrate that tropical seabird species have a more delayed onset of thermoregulatory capabilities when compared with those in temperate environments, perhaps as nest sites are less thermally challenging. Nest microhabitats and behavioural thermoregulation, are likely more important during early chick development for these species.
一个物种的体温调节能力可以决定它所占据的气候生态位。其在雏鸟中的发育受到多种因素的影响。此外，有人认为晚成雏在孵化后才发展其体温调节能力，而早成雏在卵中就开始发展这方面的能力。我们研究了塞舌尔四种同域分布海鸟的体温调节发育情况；即白色的、在地面筑巢的白尾鹲（Phaethon lepturus）和在树上筑巢的白额燕鸥（Gygis alba）；以及深色羽毛、在树上筑巢的小黑头鸥（Anous tenuirostris）和在地面及树上筑巢的棕头鸥（A. stolidus）。白尾鹲有半晚成雏，而其余物种有半早成雏。从新孵化的雏鸟开始，每隔五天测量一次泄殖腔温度（T），并随时间进行比较，同时与成鸟的T值进行比较。除了白额燕鸥外，所有雏鸟的初始T值都低于雏鸟长大后测量的值。育雏停止通常与羽毛发育同时发生，T值也随之升高。所有物种雏鸟的平均T值均显著低于成鸟的平均T值，但只有在树上筑巢的白尾鹲和棕头鸥雏鸟在按五天间隔测量雏鸟T值时，与成鸟平均T值有显著差异。对于棕头鸥雏鸟的T值，巢址和年龄存在显著的交互作用，但雏鸟颜色对T值没有显著影响。然而，沙丘顶部的棕头鸥雏鸟比树上筑巢的雏鸟更早保持恒定的T值。我们的研究结果表明，与温带环境中的海鸟相比，热带海鸟物种体温调节能力的起始发育更为延迟，这可能是因为巢址的热挑战性较小。对于这些物种来说，巢微生境和行为体温调节在雏鸟早期发育过程中可能更为重要。
