Long-term trends in first arrival and first egg laying dates of some migrant and resident bird species in northern Italy

Abstract

Climate change is affecting the phenology of seasonal events in Europe and the Northern Hemisphere, as shown by several studies of birds' timing of migration and reproduction. Here, we analyse the long-term (1982-2006) trends of first arrival dates of four long-distance migratory birds [swift (Apus apus), nightingale (Luscinia megarhynchos), barn swallow (Hirundo rustica), and house martin (Delichon urbicum)] and first egg laying dates of two migrant (swift, barn swallow) and two resident species [starling (Sturnus vulgaris), Italian sparrow (Passer italiae)] at a study site in northern Italy. We also addressed the effects of local weather (temperature and precipitation) and a climate index (the North Atlantic Oscillation, NAO) on the interannual variability of phenological events. We found that the swift and the barn swallow significantly advanced both arrival and laying dates, whereas all other species did not show any significant temporal trend in either arrival or laying date. The earlier arrival of swifts was explained by increasing local temperatures in April, whereas this was not the case for arrival dates of swallows and first egg laying dates of both species. In addition, arrival dates of house martins were earlier following high NAO winters, while nightingale arrival was earlier when local spring rainfall was greater. Finally, Italian sparrow onset of reproduction was anticipated by greater spring rainfall, but delayed by high spring NAO anomalies, and swift's onset of reproduction was anticipated by abundant rainfall prior to reproduction. There were no significant temporal trends in the interval between onset of laying and arrival in either the swift or the barn swallow. Our findings therefore indicate that birds may show idiosyncratic responses to climate variability at different spatial scales, though some species may be adjusting their calendar to rapidly changing climatic conditions.

Patterns of spring arrival dates differ in two hirundines

“…Migration timing can be modified by evolutionary processes, because arrival time affects the time of breeding (Turner 1982, Tryjanowski et al 2004, Newton 2007, Rubolini et al 2007). The link between spring migration and breeding is probably due to changes in food sources.…”

“…Most likely, migration is faster because environmental conditions during migration have improved (Huin & Sparks 1998, Gordo et al 2005, Rubolini et al 2007). However, it appears clear that sand martins are arriving now considerably earlier than barn swallows, seem more temperature responsive, and appear to have had a greater supra-temperature change.…”

Lagged influence of North Atlantic Oscillation on population dynamics of a Mediterranean terrestrial salamander

“…The effects of the NAO on local weather are observable throughout the year, but this index shows its greatest level of variability during wintertime, when the air masses that cross the Atlantic embed their highest energy content (Stenseth et al 2003). For these reasons, the NAO is mainly considered a winter climatic index, although it may influence weather conditions of western Europe (Hurrell and van Loon 1997;Stenseth et al 2003) and the Mediterranean basin (Rubolini et al 2007;Cañellas et al 2010) all over the year. In the Mediterranean, the influence of the NAO on local weather has been demonstrated in relation to air and sea temperatures, precipitations and river discharges (e.g.…”

Temperature and rainfall anomalies in Africa predict timing of spring migration in trans-Saharan migratory birds

“…Several studies that have investigated interannual variation in first or mean arrival dates at the breeding grounds in relation to ecological (mainly thermal) conditions at destination upon arrival or along the migration route have demonstrated that in years with relatively high spring temperatures migrants arrive earlier (Huin & Sparks 1998, Loxton et al 1998, Sokolov et al 1998, Sparks & Mason 2001, Tryjanowski et al 2002, Croxton et al 2006, Gordo & Sanz 2006, Rubolini et al 2007b, Sparks & Tryjanowski 2007. Whatever the mechanisms that allow birds to tune their arrival schedule based on current conditions 100s or 1000s of kilometres ahead, these studies suggest that birds can balance the ecological or socio-sexual costs and benefits of early departure from the wintering areas and arrival at the breeding grounds.…”