Early Life Events Carry Over to Influence Pre-Migratory Condition in a Free-Living Songbird

Conditions experienced during development can have long-term consequences for individual success. In migratory songbirds, the proximate mechanisms linking early life events and survival are not well understood because tracking individuals across stages of the annual cycle can be extremely challenging. In this paper, we first use a 13 year dataset to demonstrate a positive relationship between 1st year survival and nestling mass in migratory Savannah sparrows (Passerculus sandwichensis). We also use a brood manipulation experiment to show that nestlings from smaller broods have higher mass in the nest relative to individuals from larger broods. Having established these relationships, we then use three years of field data involving multiple captures of individuals throughout the pre-migratory period and a multi-level path model to examine the hypothesis that conditions during development limit survival during migration by affecting an individual's ability to accumulate sufficient lean tissue and fat mass prior to migration. We found a positive relationship between fat mass during the pre-migratory period (Sept–Oct) and nestling mass and a negative indirect relationship between pre-migratory fat mass and fledging date. Our results provide the first evidence that conditions during development limit survival during migration through their effect on fat stores. These results are particularly important given recent evidence showing that body condition of songbirds at fledging is affected by climate change and anthropogenic changes to landscape structure

Haste Makes Waste: Accelerated Molt Adversely Affects the Expression of Melanin-Based and Depigmented Plumage Ornaments in House Sparrows

. Costly life-history events are adaptively separated in time, thus, when reproduction is extended, the time available for molt is curtailed and, in turn, molt rate is accelerated.We experimentally accelerated the molt rate by shortening the photoperiod in order to test whether this environmental constraint is mirrored in the expression of plumage ornaments. Sparrows which had undergone an accelerated molt developed smaller badges and less bright wing-bars compared to conspecifics that molted at a natural rate being held at natural-like photoperiod. There was no difference in the brightness of the badge or the size of the wing-bar.These results indicate that the time available for molt and thus the rate at which molt occurs may constrain the expression of melanin-based and depigmented plumage advertisements. This mechanism may lead to the evolution of honest signaling if the onset of molt is condition-dependent through the timing of and/or trade-off between breeding and molt

Biological Earth observation with animal sensors.

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Biological Earth observation with animal sensors

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Body mass, moult and migration speed of the Goldcrest Regulus regulus in relation to the timing of migration at different sites of the migration route

We studied body mass, fat reserves and moult data of the Goldcrest Regulus regulus in re-lation to calendar date at three sites along the migration route: Gumbaritsy, NW Russia (south-eastern coast of Lake Ladoga), Kabli, SW Estonia (eastern coast of the Baltic Sea) and Rybachy, Courish Spit (eastern coast of the Baltic Sea, Russia). We analyzed migra-tion speed using ringing data obtained at these stations. The percentage of moulting birds involved in migration was higher in the northern site Gumbaritsy as compared with the southerly site (Kabli). During migration, body mass increased seasonally in the Goldcrests trapped in Gumbaritsy in 2001, but at the more southern trapping sites this trend was absent (Kabli) or recorded only in the later part of migration (Rybachy). Median fat reserves peaked in Gumbaritsy. Migration speed was affected by time pressure (i.e., it increased with date during migration and was more pronounced in the north) and the posi-tion of a certain part of migration route. Migration speed was significantly higher along the routes that crossed the Baltic Sea than at coastal routes. Birds that gained more fat at the time of ringing migrated with a higher speed