MELMAN D & JONKER N (2022) An exploratory investigation into the function of pre-breeding roosts of Black-tailed Godwits Limosa limosa. LIMOSA 95 (2): 96-104.
After returning from their wintering grounds, Black-tailed Godwits spend several weeks at roosts before spreading out over their breeding grounds (or migrating to Iceland, as for
Icelandic Godwits Limosa l. islandica). We have conducted an exploratory study to investigate the foraging ecology of Black-tailed Godwits that stage at the roost "Het Landje van Gruijters", located near the city of Haarlem and "De Hooge Weide" near the town of Castricum. Both sites consist of grassland with a shallow pool of some hundreds square
meters of about 15 cm deep. Based on a day-round count, we estimate for "Gruijters"-
pool that 400 000 mosquito larvae Chironomidae are consumed per day by a group of 150 Black-tailed Godwits.
This corresponds roughly to a third of their daily energy requirements. So, chironomids seem staple food here. However, for the comparable site at "De Hooge Weide" mosquito larvae intakes were much lower, while the mosquito larvae supply was comparable. At this site grassland was preferred for foraging on earthworms.
It is conceivable that this difference is partly determined by the surroundings of the roost: the grassland around "Landje van Gruijters" (intensively managed) might be less attractive
than the grassland of "De Hooge Weide" (extensively managed). To test these ideas, information on earthworm intake rates on the grasslands would be required. Research on the food intake by birds lends itself to a citizen-science approach, in which citizens collect standardized data on foraging birds on grassland. This way a first impression could be obtained of the functioning of different grassland-parcels for meadow birds.
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