Intra-seasonal changes in local pattern of Corncrake Crex crex occurrence require adaptive conservation strategies in Alpine meadows

Abstract

SummaryAs a double-brooded species inhabiting grassland habitats subject to mowing and located at different elevations, the Corncrake Crex crex in the Alps is potentially affected by changes in its breeding habitat within a season, thus leading to shifts in occurrence and habitat association, with potentially relevant consequences for conservation. We investigated Corncrake abundance in four sites in Trento province (N Italy); two sites were defined as 'low elevation' (mean elevation 975 m and 976 m a.s.l., respectively) and two as 'high elevation' (mean elevation 1,173 m and 1,177 m). The number of calling males showed a clear variation in relative abundance between early and late periods of the breeding season; in particular, at low elevation sites, abundance decreased from the early to late periods, while the opposite was recorded at high elevation sites. A mixed model suggested that the number of males decreased in the second half of the breeding season and at high elevations, and changed according to mid-season altitudinal shifts. Conservation strategies for this species should take into account the mid-season territory shift.

The introduction of subsidies for grassland conservation in the Italian Alps coincided with population decline in a threatened grassland species, the CorncrakeCrex crex

“…We avoided rainy and windy days. Field tests at the beginning of the research revealed how the number of males counted in consecutive field sessions before mowing was fairly constant, suggesting high vocal activity and detection rate (P. Pedrini et al unpublished data), as found for other rallids (Brambilla & Jenkins 2009); previous analyses revealed weak effects of census date within the survey period (Brambilla & Pedrini 2011). Not all the areas were visited each year; out of 84 cases, early count data were available for 73 areas/years, and late count data for 60.…”

“…We separately considered early and late counts because of within-season habitat and distribution (from low to high elevation) shifts (Brambilla & Rubolini 2009, Gilroy et al 2010, Brambilla & Pedrini 2011, which can affect the estimation of population trends . We expected an almost immediate effect of changes in mowing practices introduced by subsidies on the population trend for late season data, and a weaker or delayed effect for early season data.…”

Habitat management effects on Prealpine grassland bird communities

“…A sudden change in sward height and structure due to haymaking, leading to large areas with short and homogeneous vegetation, may also make small passerines more vulnerable to predators (Vickery et al 2001). Moreover, mid-season mowing is causing population declines of threatened grassland species, such as the corncrake (Crex crex Linnaeus, 1758) in the Eastern Alps (Brambilla & Pedrini 2011). Low-intensity grazing by free-ranging livestock may instead help to prevent natural vegetation dynamics, including growth of shrubs and trees, without severely reducing habitat heterogeneity (Nikolov 2010).…”

“…Such measures could provide financial support to small farms with free-ranging livestock (the so-called "alpeggio" system). However, this may not be sufficient, since grassland species require unmown grassland patches until the end of the breeding season, and mowing should be postponed as much as possible to enhance breeding success and improve suitability of managed grasslands (Müller et al 2005;Brambilla & Pedrini 2011). Financial subsidies for the maintenance of the "alpeggio" system are already provided in the Lombardy Region within the framework of the Rural Development Plan (Allegato I, Decreto n. 970, issued on 13 February 2012, in Italian).…”

The effects of habitat and spatial features of wetland fragments on the abundance of two rallid species with different degrees of habitat specialization

“…Until some decades ago, wetland habitats were much more widespread, occupying large areas in river valleys; however, drying-out and intensification of agricultural practices led to widespread wetland destruction. Wetland sites are thus currently limited to residual patches, and most riparian habitats have been destroyed; this is the likely cause of the extinction of some other rallid species (regional population of Spotted Crake Porzana porzana and wetland population of Corncrake Crex crex [Pedrini et al 2005, Brambilla & Pedrini 2011, Pedrini et al 2012). We considered 28 wetlands scattered over the whole Province (Fig.…”