Long‐term changes in autumn migration dates at the Strait of Gibraltar reflect population trends of soaring birds

Abstract

A growing body of work shows that climate change is the cause of a number of directional shifts in the spring phenology of migratory birds. However, changes in autumn phenology are well studied and their consistency across species, as well as their link with population trends, remains uncertain. We investigate changes in the autumn migration dates of 11 species of soaring birds over the Strait of Gibraltar over a 16‐year period. Using models corrected for phylogeny, we assessed whether ecological and morphological characteristics, as well as population trends, account for interspecific shifts in migration times. We recorded different phenological changes in different periods of the migration season and suggest that these differences are due to age‐dependent responses. The variable best predicting advances in migration dates was population trend: species that did not advance their autumn migration dates were those showing a decline in their European breeding populations. We repeated our tests on a dataset representing the migration date of soaring birds across the Pyrenees Mountains and found that population trends at this site also predicted phenological shifts. Our results suggest that flexibility in migratory strategy and population trends may be related, such that different adaptive capacity in migration timing may be more relevant than other ecological traits in determining the conservation status of migratory birds in Europe and perhaps other regions.

Different trends of neighboring populations of Lesser Kestrel: Effects of climate and other environmental conditions

“…Climate change is threatening the long‐term persistence of many populations of migratory birds (Jiguet, Gadot, Julliard, Newson, & Couvet, ; Møller, Rubolini, & Lehikoinen, ; Panuccio, Martin, Morganti, Onrubia, & Ferrer, ; Stephens et al, ). In this scenario, our findings suggest that the fate of populations with different climate sensitivity may also differ.…”

Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America

“…One common way to monitor populations of birds of prey is by tracking migratory movement at watch sites and banding stations along migratory flyways [5,13,14]. Long-term data sets from raptor migration watch-sites can indicate population dynamics for specific species and populations, which can provide indications of changes in population size [15][16][17][18][19]. However, it can be difficult to connect migrating birds to other geographic stages in their life cycle (breeding and wintering) through these data, and without these connections it may be problematic to understand what factors underlie population size changes [20].…”

“…In this study, we used the variation in δ 2 H F and δ 18 O F values of A. striatus and large scale models of spatial isotopic variation (isoscapes)for hydrogen and oxygen to: a) examine the origin of A. striatus caught along the Pacific Coast Flyway in comparison to birds caught along the Intermountain Flyway, and b) investigate the usefulness of oxygen isotopes to determine the origin of raptorial birds of prey. First, we established relationships, separately for hydrogen and oxygen, between δ 2 H F and δ 18 O F values of A. striatus museum specimens from known natal locations, to predict the isotope values of precipitation at the origin regions of birds migrating along the Pacific Coast and Intermountain Flyways from the measured isotope values of migrant's feathers. Prediction of precipitation hydrogen and oxygen isotope composition and assignment of migrating bird origin locations were accomplished using an internet-based environmental water isoscape of Western North America (http://isomap.org) [55].…”

“…Prediction of precipitation hydrogen and oxygen isotope composition and assignment of migrating bird origin locations were accomplished using an internet-based environmental water isoscape of Western North America (http://isomap.org) [55]. Finally, predictions of sites of origin based on δ 2 H P and δ 18 O P values were also compared.…”

Migrating raptor counts: the need for sharing objectives and field protocols, and the benefits of using radar

“…Interest in counting migrating raptors also emerged in other countries as a stand against raptor slaughter; this was the case with some Mediterranean countries, such as Italy and Malta (Sultana & Gauci 1982, Giordano 1991, Panuccio 2005. Today, long-term projects of raptor counts are considered a valuable tool for detecting population trends at regional and continental scales (Agostini et al 2007, Martin et al 2016, but also to investigate the influence of climate change on the ecology of raptors, especially with respect to migration timing (Filippi-Codaccioni et al 2010, Jaffré et al 2013, Panuccio et al 2016a. This method is considered to be cost-effective, because birds of prey are usually secretive and at low densities when breeding and therefore are difficult to survey at that time, in particular over large spatial scales, while soaring species concentrate along definitive flyways during migration (Bildstein 2006.…”