Non‐breeding areas and timing of migration in relation to weather of Scottish‐breeding common sandpipers Actitis hypoleucos

Abstract

The number of breeding common sandpipers has declined in Britain due to poorer return rates from non‐breeding areas. To investigate little known aspects of their annual cycle, breeding common sandpipers were fitted with geolocators to track their migrations and determine their non‐breeding areas. Ten tagged birds left Scotland on 9 July (median dates and durations are given throughout the abstract). Short‐term staging was carried out by some birds in England and Ireland, then for longer by most birds in Iberia before continuing to West Africa, arriving on 28 July. Six birds spent most of the non‐breeding season (October–February) on the coast of Guinea‐Bissau, suggesting that this is a key area. Single birds occurred in Sierra Leone, Guinea, the Canary Islands and western Sahara. The southward migration from Scotland took 17.5 d (range 1.5–24 d), excluding the initial fuelling period. The first northward movement from Africa was on 12 April. Staging occurred in either Morocco, Iberia or France. Arrival in Scotland was on 2 May. The northward migration took 16 d (range 13.5–20.5 d). The main migration strategy involved short‐ and medium‐range flights, using tail‐winds in most cases. Variation in strategy was associated with departure date; birds that left later staged for shorter durations. Coastal West Africa provides two major habitats for common sandpipers: mudflats associated with mangroves and rice fields. Although the area of mangrove has been depleted, the scale of loss has probably been insufficient to account for the decline in sandpiper numbers. Rice fields are expanding, providing feeding areas for water‐birds. Meteorological data during the migrations suggest that the weather during the southward migration is unlikely to contribute to a population decline but strong cross‐winds or head‐winds during the northward migration to the breeding grounds may do so.

Migrating Curlews on Schedule: Departure and Arrival Patterns of a Long-distance Migrant Depend on time and Breeding Location Rather than on Wind Conditions

“…Low impact of weather effects Surprisingly, our ndings provided no evidence for weather as a migration trigger in curlews, in contrast to various other bird species [12,24,[31][32]. However, our data con rmed that ight speed increased with increasing TWC, in accordance with previous studies [6,29].…”

“…We proposed ve hypotheses. (1) Given that tailwinds will increase ight and migration speeds [6; 29-30], we expected curlews to time their departure from and arrival at their wintering grounds according to favourable wind and weather conditions, especially in relation to tailwind conditions, lack of precipitation, and air temperature, as found in other bird species [12,24,[31][32]. (2) In line with this, we expected ight heights (as recorded by GPS tags) to increase during non-tailwind conditions to allow the birds to reach air layers with improved wind conditions [22,33].…”

Migrating Curlews on Schedule: Departure and Arrival Patterns of a Long-Distance Migrant Depend on Time Rather than on Wind Conditions

“…(2) Individuals of a range of bird species have been shown to time their departure according to favourable wind and weather conditions (e.g. a tailwind and no or little precipitation; [12,[22][23][24]. In line with our rst hypothesis, we therefore expected curlews to time their departure from and arrival at their wintering grounds according to favourable wind and weather conditions, especially in relation to tailwind conditions and lack of precipitation.…”

“…However, in contrast to our assumption, the current study revealed virtually no effect of wind or other weather parameters on the departure/arrival day for curlews, even when the actual weather during departure was compared with the mean weather conditions 4 days and/or 4 years prior to departure. Although curlews rarely departed during hours with precipitation (in accordance with other bird species) [12,[23][24], this predictor had no signi cant in uence in our nal model. The current ndings were therefore not in agreement with previous studies, which found that the probability of departure of curlews from a pre-breeding staging site was reduced during precipitation [46].…”

The effects of geolocators on return rates, condition, and breeding success in Common Sandpipers Actitis hypoleucos

“…These individuals were carrying thinner and lighter tags than those tagged in the UK. The only other study to attach geolocators to Common Sandpipers using leg flags did not report any adverse effects, but used tags similar in size and weight to those we deployed in Senegal (Summers et al 2019). Given the prevalence of tracking studies carried out on many different species, it is surprising that no others that we know of have reported tags causing limb loss.…”