Bearded Reedlings Adjust Their Pair-Bond Behaviour in Relation to the Sex and Attractiveness of Unpaired Conspecifics

An individual's investment in mating or keeping a pair bond intact may be influenced not only by the attractiveness of its current mate, but also by that of other potential mates. In this study, we investigated the effect of relative attractiveness on pair-bond behaviour in bearded reedlings, Panurus biarmicus. We showed that mate attractiveness, in terms of beard length in males and tail length in females, influenced courtship behaviour when the pair was kept isolated. In the presence of a conspecific, contact initiations within a pair increased. This increment was mainly related to the sex of the unpaired conspecific, however, and less to differences in attractiveness between the current partner and the unpaired conspecific. Female contact initiations towards potential extra mates were independent of male attractiveness, whereas male contact behaviour was significantly influenced by female attractiveness. However, females displayed more contact initiations to their current mate when they were less attractive than the unpaired females. Males decreased their overtures towards other females with increasing attractiveness of their current mates. Overall, our results suggested that, when there was a risk of losing their mate, bearded reedlings adjust their pair-bond investment mainly in response to the presence or absence of a competitor, and fine-tune investment to a lesser extent in response to the attractiveness of that potential competitor

The effect of extreme spring weather on body condition and stress physiology in Lapland longspurs and white-crowned sparrows breeding in the Arctic

AbstractClimate change is causing rapid shifts in temperature while also increasing the frequency, duration, and intensity of extreme weather. In the northern hemisphere, the spring of 2013 was characterized as extreme due to record high snow cover and low temperatures. Studies that describe the effects of extreme weather on phenology across taxa are limited while morphological and physiological responses remain poorly understood. Stress physiology, as measured through baseline and stress-induced concentrations of cortisol or corticosterone, has often been studied to understand how organisms respond to environmental stressors. We compared body condition and stress physiology of two long-distance migrants breeding in low arctic Alaska – the white-crowned sparrow (Zonotrichia leucophrys) and Lapland longspur (Calcarius lapponicus) – in 2013, an extreme weather year, with three more typical years (2011, 2012, and 2014). The extended snow cover in spring 2013 caused measureable changes in phenology, body condition and physiology. Arrival timing for both species was delayed 4–5days compared to the other three years. Lapland longspurs had reduced fat stores, pectoralis muscle profiles, body mass, and hematocrit levels, while stress-induced concentrations of corticosterone were increased. Similarly, white-crowned sparrows had reduced pectoralis muscle profiles and hematocrit levels, but in contrast to Lapland longspurs, had elevated fat stores and no difference in mass or stress physiology relative to other study years. An understanding of physiological mechanisms that regulate coping strategies is of critical importance for predicting how species will respond to the occurrence of extreme events in the future due to global climate change

Data for: An exception to the rule: captivity does not stress wild migrating northern wheatears

The raw data set as used for the statistical analyses

Oxidative damage to lipids is rapidly reduced during migratory stopovers

Most migrating birds need to stopover in between flights in order to refuel. Lately, additional purposes of stopover have been suggested, including physiological recovery from metabolically demanding migratory flight. One apparently unavoidable, but harmful physiological effect of migratory flight is increased oxidative damage to lipids and proteins. We here, for the first time, tested whether migrating birds are able to reduce their oxidative damage during stopover. To be able to collect longitudinal data on a large number of individual birds, we temporarily caged wild northern wheatears, a long-distance migrant which does not suffer stress when caged during migration. Around noon on the first and third day at stopover, the birds were blood-sampled to determine malondialdehyde (MDA) concentration, a commonly used marker of oxidative damage to lipids. We found that MDA concentrations significantly decreased during stopover, a result unchanged when correcting for the peroxidizability of the substrate. The extent of the decrease was unrelated to the amounts of food consumed or of fuel accumulated. Our findings support the hypothesis that stopovers serve reduction of oxidative damage, warranting re-thinking of how birds accomplish their migrations. They also highlight the need to include physiological recovery as a driver of the (temporal) organization of migration. A free Plain Language Summary can be found within the Supporting Information of this article

Data for: An exception to the rule: captivity does not stress wild migrating northern wheatears

The raw data set as used for the statistical analyses.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV