Montagu\u2019s Harrier breeding parameters in relation to weather, colony size and nest protection schemes: a long-term study in Extremadura, Spain

C. Giovanni Galizia,Beatriz Arroyo,Brigitte Berger-Geiger

doi:10.1007/s10336-018-1618-0

C. Giovanni Galizia, Beatriz Arroyo + Show 1 more

Open Access

https://doi.org/10.1007/s10336-018-1618-0

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Abstract

On the basis of long-term (2001–2017) and extensive data (> 1700 breeding attempts), we assess factors influencing breeding parameters in Montagu’s Harrier (Circus pygargus), a medium-sized ground-nesting semi-colonial raptor breeding in cereal fields, in a study area in its core distribution range (Extremadura, Spain). We evaluated annual and long-term variation in breeding parameters, as well as changes in environmental variables such as weather or harvest date. We then evaluated breeding failure and productivity in relation to nest protection measures, weather conditions, lay date and colony size. We found a significant trend for productivity to decrease over the 17-year study period, associated with a trend for predation probability to increase over time. Harvest occurred increasingly earlier in more recent years. The success rate of nests protected with unfenced unharvested patches (the most frequently used protection measure) increased with harvest date, but also declined throughout the study period for equivalent harvest dates. When considering all explanatory variables together, probability of nest success decreased significantly with lay date and throughout the study period, increased with annual rainfall and varied in relation to protective measures (being highest for nests protected with fences or where harvest in the plot had been delayed). In addition, among successful nests, fledged brood size also decreased significantly with lay date and temperature, and increased with annual rainfall. We found no effect of number of neighbours on breeding output. We discuss our results in relation to future conservation prospects for the species.

Highlights

Knowledge about factors influencing breeding parameters is essential to understand population dynamics and to design management strategies for species of conservation concern
We found a significant trend for success rate to decrease and predation rate to increase with lay date ( 12 = 35.58, P < 0.0001, slope − 0.048 ± 0.008 and 12 = 33.99, P < 0.0001, slope − 0.049 ± 0.009 respectively) and throughout the study period (Table 3, Fig. 3)
As in many other species (Newton and Marquiss 1984; Pietiäinen 1989; Meijer et al 1990; Sæther 1990), we found a strong relationship between lay date and breeding output, with productivity being lower for later-breeding pairs

Summary

Introduction

Knowledge about factors influencing breeding parameters is essential to understand population dynamics and to design management strategies for species of conservation concern. Both biotic and abiotic factors affect breeding in birds. Habitat quality is an essential factor affecting breeding in most species. Among non-biotic factors, weather is a limiting factor for many species, and studying the relationships between weather and breeding is important, in view of recent climate change (Moss et al 2001; Carvalho et al 2011). Human intervention as part of conservation schemes may influence breeding in managed species, and assessing this is important in order to evaluate efficiency of use of conservation resources (Sutherland et al 2004)

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