Thermal consequences of turning white in winter: a comparative study of red grouse Lagopus lagopus scoticus and Scandinavian willow grouse L. l. lagopus

Abstract

Thermal consequences of turning white in winter: a comparative study of red grouse Lagopus lagopus scoticus and Scandinavian willow grouse L. l. lagopus. -Wildl. Biol. 13: 120-129.The red grouse Lagopus lagopus scoticus differs from the willow grouse L. l. lagopus of mainland Europe in not developing a white winter plumage. Previous studies have suggested that plumage colouration in birds can have important consequences for heat transfer through the feather layer. We examined the thermal consequences of plumage colouration in both subspecies of grouse. There were no differences in feather density, plumage depth or thermal resistance of the plumage between dark rufous Scottish and white Scandinavian grouse. In still air, heat gained from simulated solar radiation was greater through dark than through white plumage. However, in wind there was no difference in heat load between dark and white plumages. Our study suggests that there may be a tradeoff between thermal and camouflage benefits of plumage colour for grouse in the wild.

Applications of thermal imaging in avian science

“…, Ward et al . ). More realistic measures of metabolic heat loss and operative temperature of birds can be made using heated taxidermic mounts (Bakken et al .…”

Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world?

“…In rock ptarmigan, winter white plumage may be longer and denser than summer plumage (Salomonsen, ), but no difference in mass was found in rock ptarmigan in Norway (Mortensen, Nordøy, & Blix, ). Furthermore, density or plumage depth were similar between white willow ptarmigan and red grouse, implying no differences in thermal resistance and minimal differences in heat gain (Ward et al, ).…”

A phylogenetic comparative analysis reveals correlations between body feather structure and habitat

“…Second, by varying the composition, microoptical and microstructural properties of plumage (i.e., color, relative densities of different feather types, morphologies of body feathers), water repellency, and insulatory functions can also be controlled (e.g., Rijke ; Middleton ; Wolf & Walsberg ; Ward et al . ; Broggi et al . ; Rijke & Jesser ; Pap et al .…”

“…The basic, non-flight related, functions of bird body feathers are twofold: First, by varying the number of feathers per surface area, the amount of trapped air, and hence water resistance and thermo-conductivity, can be controlled (e.g., Middleton 1986;Swanson 1991;Fernando Novoa, Bozinovic & Rosenmann 1994;Cooper 2002;Williams, Hagelin & Kooyman 2015). Second, by varying the composition, microoptical and microstructural properties of plumage (i.e., color, relative densities of different feather types, morphologies of body feathers), water repellency, and insulatory functions can also be controlled (e.g., Rijke 1970;Middleton 1986;Wolf & Walsberg 2000;Ward et al 2007;Broggi et al 2011;Rijke & Jesser 2011;Pap et al 2015;Williams, Hagelin & Kooyman 2015;Koskenpato et al 2016). These different functions are immediately evident in different species; the Emperor Penguin (Aptenodytes forsteri), for example, has a particular spatial pattern and ratio of different feather types, including body and attached after-feathers, filoplumes, and downy feathers that make its body covering uniquely insulative and suited to its lifestyle (Williams, Hagelin & Kooyman 2015), while diving Great Cormorants (Phalacrocorax carbo) balance body feather structures between waterproofing and wettability to fulfil requirements of insulation and reduced buoyancy during diving (Rijke 1968;Gr emillet et al 2005).…”