Browsing by Author "Grond, K."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Prey type and foraging ecology of Sanderlings Calidris alba in different climate zones: Are tropical areas more favourable than temperate sites?(PeerJ, 2015-08) Grond, K.; Ntiamoa-Baidu, Y.; Piersma, T.; Reneerkens, J.Sanderlings (Calidris alba) are long-distance migratory shorebirds with a non-breeding range that spans temperate and tropical coastal habitats. Breeding in the High Arctic combined with non-breeding seasons in the tropics necessitate long migrations, which are energetically demanding. On an annual basis, the higher energy expenditures during migration might pay off if food availability in the tropics is higher than at temperate latitudes. We compared foraging behaviour of birds at a north temperate and a tropical non-breeding site in the Netherlands and Ghana, respectively. In both cases the birds used similar habitats (open beaches), and experienced similar periods of daylight, which enabled us to compare food abundance and availability, and behavioural time budgets and food intake. During the non-breeding season, Sanderlings in the Netherlands spent 79% of their day foraging; in Ghana birds spent only 38% of the daytime period foraging and the largest proportion of their time resting (58%). The main prey itemin the Netherlands was the soft-bodied polychaete Scolelepis squamata, while Sanderlings in Ghana fed almost exclusively on the bivalve Donax pulchellus, which they swallowed whole and crushed internally. Average availability of polychaete worms in the Netherlands was 7.4 g ash free dry mass (AFDM)m-2, which was one tenth of the 77.1 g AFDMm-2 estimated for the beach in Ghana. In the tropical environment of Ghana the Sanderlings combined relatively low energy requirements with high prey intake rates (1.64 mg opposed to 0.13 mg AFDM s-1 for Ghana and the Netherlands respectively). Although this may suggest that the Ghana beaches are the most favourable environment, processing the hard-shelled bivalve (D. pulchellus) which is the staple food could be costly. The large amount of daytime spent resting in Ghana may be indicative of the time needed to process the shell fragments, rather than indicate rest. © 2015 Grond et al.Item Sanderlings using African-Eurasian flyways: a review of current knowledge(Wader Study Group Bulletin 116 (1): 2-20, 2009) Reneerkens, J.; Benhoussa, B.; Boland, H.; Collier, M.; Grond, K.; Günther, K.; Hallgrimsson, G.T.; Hansen, J.; Meissner, W.; De Meulenaer, B.; Ntiamoa-Baidu, Y.; Piersma, T.; Poot, M.; van Roomen, M.; Summers, R.W.; Tomkovich, P.S.; Underhill, L.G.Despite the worldwide occurrence of Sanderlings Calidris alba on popular beaches, strikingly little is known about their biology compared to other common waders. Here we review the limited available knowledge of Sanderlings that use African–Eurasian flyways. The basis for this review was a workshop on Sanderlings, held during the International Wader Study Group conference in Jastrzębia Góra, Poland in 2008. We focus on biogeography,trends, numbers, diet, migration patterns and reproduction. Gaps in our knowledge are identified and we discuss the evidence for a Siberian origin of Sanderlings wintering in NW Europe, and plead for more non-estuarine surveys and collaboration between colour-ring projects both in space and time to get a better understanding of population dynamics and migration phenology.Item Why do some Sanderlings Calidris alba winter in the Wadden Sea while others prefer tropical beaches?(Limosa, 2009-12) Reneerkens, J.; Grond, K.; Koomson, E.; Ntiamoa-Baidu, Y.; Piersma, T.Sanderlings Calidris alba occur worldwide along sandy beaches and have a wide range of non-breeding locations in different climate zones. Previous studies clearly indicated that ambient temperatures have profound effects on daily energy expenditures of Sanderlings. In this study we investigated the foraging ecology of Sanderlings on beaches near Esiama, Ghana and on the Wadden Sea island of Vlieland, The Netherlands. The diet was very different at the two locations. In Vlieland the birds fed predominantly on the polychaete Scolelepis squamata whereas a small shellfish Donax rugosus was taken in Esiama (Fig. 4,5). The latter prey item was very abundant in Esiama where a band of 2-14 m width containing densities of 5,700-14,300 individuals per m2 occurred. This resulted in caloric energy intake rates of 8 kJ/h foraging time in Vlieland and 130 kJ/h in Ghana. On Vlieland the birds spent on average 79% of their time foraging and in Esiama this was only 36% and most time (58 %) was spent resting (Fig. 2). We argue, however, that during the long resting breaks on roosts, Sanderlings in Ghana were in fact digesting and emptying their gut and intestines from indigestable shell remains. During future studies we plan to study annual and seasonal survival of sanderlings wintering at different latitudes in relation to disease risk and prédation probability.