Forecasting spring from afar? Timing of migration and predictability of phenology along different migration routes of an avian herbivore

Abstract

and 8 Vogeltrekstation -Dutch Centre for Avian Migration and Demography (NIOO-KNAW), 6708 PB Wageningen, The Netherlands Summary 1. Herbivorous birds are hypothesized to migrate in spring along a seasonal gradient of plant profitability towards their breeding grounds (green wave hypothesis). For Arctic breeding species in particular, following highly profitable food is important, so that they can replenish resources along the way and arrive in optimal body condition to start breeding early. 2. We compared the timing of migratory movements of Arctic breeding geese on different flyways to examine whether flyways differed in the predictability of spring conditions at stopovers and whether this was reflected in the degree to which birds were following the green wave. 3. Barnacle geese (Branta leucopsis) were tracked with solar GPS/ARGOS PTTs from their wintering grounds to breeding sites in Greenland (N = 7), Svalbard (N = 21) and the Barents Sea (N = 12). The numerous stopover sites of all birds were combined into a set of 16 general stopover regions. 4. The predictability of climatic conditions along the flyways was calculated as the correlation and slope between onsets of spring at consecutive stopovers. These values differed between sites, mainly because of the presence or absence of ecological barriers. Goose arrival at stopovers was more closely tied to the local onset of spring when predictability was higher and when geese attempted breeding that year. 5. All birds arrived at early stopovers after the onset of spring and arrived at the breeding grounds before the onset of spring, thus overtaking the green wave. This is in accordance with patterns expected for capital breeders: first, they must come into condition; at intermediate stopovers, arrival with the food quality peak is important to stay in condition, and at the breeding grounds, early arrival is favoured so that hatching of young can coincide with the peak of food quality. 6. Our results suggest that a chain of correlations between climatic conditions at subsequent stopovers enables geese to closely track the green wave. However, the birds' precision of migratory timing seems uninfluenced by ecological barriers, indicating partly fixed migration schedules. These might become non-optimal due to climate warming and preclude accurate timing of long-distance migrants in the future.

Forage plants of an Arctic‐nesting herbivore show larger warming response in breeding than wintering grounds, potentially disrupting migration phenology

“…Contrastingly, food peaks are unlikely to advance at temperate sites under warming up to 1.7°C, as out warming treatment did not affect plant growth. The larger warming response of Arctic forage plants which we find can more strongly advance peaks in food availability further along the migratory flyway and thus give rise to mismatches between bird migration and peak food availability (Doiron et al., 2015; Kölzsch et al., 2015; Meltofte et al., 2007). …”

“…Under a shortening of this period, geese might not have the time to both exploit temperate food peaks prior to migration and still arrive on the breeding grounds on time (Meltofte et al., 2007). Also, as geese time their spring migration according to peaks of nitrogen (van der Graaf et al., 2006), the lack of advancement of food peaks in temperate regions could deteriorate the ability of the geese to predict food conditions on the Arctic breeding grounds (Kölzsch et al., 2015). Either one or the combination of these effects is likely to result in a mismatch between goose migration phenology and peak food availability (Dickey et al., 2008), which has been shown to strongly reduce gosling growth (Doiron et al., 2015).…”

“…This is a well‐known model system to study bird migratory timing in relation to the green wave (Shariatinajafabadi et al., 2014; van der Graaf et al., 2006) and climatic variables (Kölzsch et al., 2015). Our study sites are located in preferred feeding salt marsh habitats at three sites along this migratory flyway: one temperate wintering site, one temperate spring stopover site, and one Arctic breeding site (Figure 1).…”

“…Such a mismatch in intertrophic relationships can have large consequences for reproductive success and, ultimately, population size (Both & Visser, 2001; Miller‐Rushing, Hoye, Inouye, & Post, 2010; Møller et al., 2008; van Gils et al., 2016). Migratory species are more vulnerable to these mismatches, as changes in climate are often not correlated between their wintering sites and breeding grounds (Emmenegger et al., 2016; Kölzsch et al., 2015). In the Arctic region, climate warming is expected to be more severe than the global average, a process called arctic amplification (Serreze, Barrett, Stroeve, Kindig, & Holland, 2009; Stocker et al., 2013), and rapid advancement of the onset of spring inducing strong phenological responses of plants and animals are already found in the Arctic (Høye, Post, Meltofte, Schmidt, & Forchhammer, 2007; Post et al., 2009).…”

Migration timing and stopover selection for barnacle geese Branta leucopsis

“…Moreover, the timing of the Russian geese migration from the Baltic Sea was not linked to the advancement of plant growth, most likely because of the low correlation in the weather patterns between the Baltic Sea and White Sea (van der Graaf, 2006). Using the third derivative of daily temperature sums (GDDjerk), Kölzsch et al (2015) showed that the geese are able to closely follow the green wave during their spring migration if predictability of climatic conditions was high between stopovers. Therefore, in the case that predictability is low, the geese might rely more on fixed cues such as photoperiod (length of daylight hours), and do not migrate earlier in the year if spring is early.…”