The relative importance of food abundance and weather on the growth of a sub-arctic shorebird chick

Abstract

Understanding how environmental conditions affect growth is important because conditions experienced during early development could have immediate as well as long-term fitness consequences. Annual fluctuations in (environmental) conditions may influence life histories of entire cohorts of offspring. In birds, food availability and weather have been identified to affect chick growth. However, the relative importance of these factors in explaining growth in different years is poorly understood. We studied the growth of golden plover Pluvialis apricaria chicks by radio-tracking individuals from hatching till fledging and related variation in chick growth to food availability (as sampled by pitfall trapping) and weather conditions. 2011 appeared to be a favourable season in which the chicks achieved notably fast growth rates. In 2013, in contrast, chicks were lagging behind in growth and possibly even achieved smaller ultimate sizes. Food abundance had a dominant effect on growth, whereas temperature only had short-term effects (at least in body weight). Thus, variation in food availability rather than variation in weather could explain the marked difference in growth of the plover chicks between the years. A short but intense flush of Bibio flies late in the breeding season in 2011 seems the reason why the plover chicks managed to achieve high growth rates in that year, despite hatching after the main arthropod peak. Thus, understanding cohort effects in the growth of plover chicks, for example in relation to climate change, requires an understanding of the seasonal dynamics of individual prey species. Yearly variation in environmental conditions may influence the life histories of whole cohorts of offspring. Understanding these ‘cohort effects’ is important to ultimately understand life history evolution. We studied the growth of golden plover chicks, a sub-arctic breeding shorebird, during two breeding seasons, and found that chick growth lagged behind in 2013. In birds, food availability and weather have been identified to be the two main factors affecting chick growth, but the relative importance of these factors in explaining differences in growth between years is poorly understood. These examples are indeed needed to ultimately understand population dynamics and life history evolution in the field.