Is the denser contour feather structure in pale grey than in pheomelanic brown tawny owlsStrix alucoan adaptation to cold environments?

Abstract

In colour polymorphic species morphs are considered to be adaptations to different environments, where they have evolved and are maintained because of their differential sensitivity to the environment. In cold environments the plumage insulation capacity is essential for survival and it has been proposed that plumage colour is associated with feather structure and thereby the insulation capacity of the plumage. We studied the structure of contour feathers in the colour polymorphic tawny owl Strix aluco. A previous study of tawny owls in the same population has found strong selection against the brown morph in cold and snowy winters whereas this selection pressure is absent in mild winters. We predicted that grey morphs have a denser and more insulative plumage, enabling them to survive better in cold climate compared to brown ones. The insulative plumulaceous part of the dorsal contour feathers was larger and the fine structure of the plumulaceous part of the feather was denser in grey tawny owls than in brown ones. In the ventral contour feathers the plumulaceous part of the feather was denser in females than in males and in older birds without any differences between morphs. Our study suggests that insulative microscopical feather structures differ between colour morphs and we propose that feather structure may be a trait associated with morph‐specific survival in cold environments.

Increasing phenological asynchrony between spring green-up and arrival of migratory birds

“…Linden et al . 56 empirically evaluated parametric and nonparametric models and suggested that parametric models are most often preferable for modeling the arrival period. Regardless of the approach, however, the sensitivity of phenological interval to arrival date estimation should be evaluated, because the estimation could be influenced by data following the arrival period.…”

“…Although nonparametric 55 and parametric 9 models are both employed in phenological studies of birds, parametric models are often preferable 56 . Still, the logistic might not be appropriate if a large proportion of migrants arriving to a cell pass through, rather than remain in the cell.…”

Actogram analysis of free-flying migratory birds: new perspectives based on acceleration logging

“…Activity levels in-between will represent foraging or breeding activities—feeding/hunting, predator escape, preening, territory defence, etc., see Bäckman et al (2016) for an example of implementation of such a sampling scheme.…”

“…Needless to say, the patterns emerging for only two individuals will serve only as examples and illustrations, and conclusion about the birds’ general behaviour must await analyses based on accelerometer data from large samples of individuals. The results presented in this paper are from a red-backed shrike that was recaptured in 2016, but also include some comparisons with data from a bird recaptured in 2015 that have been presented in Bäckman et al (2016). Both of these birds were equipped with loggers in 2014 that measured activity during 2014–2015.…”

“…Logging of accelerometer data has been used for three main purposes in studies of animal behaviour—(1) for classifying behaviour and mode of locomotion and flight, (2) for estimating energy demands (these two aspects have been reviewed by Brown et al 2013) and, most recently, (3) for recording actograms of individuals in order to analyse daily and annual activity and flight patterns in bird migration. The latter has recently been made possible for small migratory birds (Liechti et al 2013; Bäckman et al 2016; Hedenström et al 2016). …”