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

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.

Does human hair attract or deter potential ground nest predators?

“…This result is expected and is not surprising, as the effectiveness of the game fence has been supported by several experiments and has therefore long been used to protect nests of ground-nesting bird species (e.g. Smith et al 2011, Homberger et al 2017, Roos et al 2018, Berger-Geiger et al 2019. Since fencing does not exclude bird predators, its use is recommended only in areas where terrestrial nest predators, primarily mammals, predominate (Sargeant et al 1993).…”

Optimized Monitoring and Conservation of Farmland Bird Species through Bayesian Modelling: The Montagu’s Harrier Circus pygargus Population in Central Italy

“…The Circus pygargus can be characterized by polygamous relationships [24][25][26], which was not considered in our model. However, we note that: (1) this species is a seasonal monogamous species, with only rare cases of polygamy [24]; (2) the elevated accuracy (>90%) of our model suggests that we have not forgotten any important predictor variable, i.e., if polygamy occurred in our breeding sites then it was sporadic or irrelevant.…”

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Protecting wild bird nests against predators: A systematic review and meta‐analysis of non‐lethal methods

“…Narango et al, 2017), exclusion of livestock or people from nesting areas (e.g. Berger-Geiger et al, 2019) or through predator control or exclusion (Smith et al, 2010(Smith et al, , 2011. The impact of nest predators can be reduced using both lethal and non-lethal techniques.…”