Intake rates and the functional response in shorebirds (Charadriiformes) eating macro-invertebrates

• Published in: Biological Reviews
• Main Authors: Goss-Custard, J.D., West, A.D., Yates, M.G., Caldow, R.W.G., Stillman, R.A., Bardsley, L., Castilla, J., Castro, M., Dierschke, V., Durell, S.E.A.L.V., Eichhorn, G., Ens, B.J., Exo, K.M., Udayangani-Fernando, P.U., Ferns, P.N., Hockey, P.A.R., Gill, J.A., Johnstone, I., Kalejta-Summers, B., Masero, J.A., Moreira, F., Nagarajan, R.V., Owens, I.P.F., Pacheco, C., Perez-Hurtado, A., Rogers, D., Scheiffarth, G., Sitters, H., Sutherland, W.J., Triplet, P., Worrall, D.H., Zharikov, Y., Zwarts, L., Pettifor, R.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2006
• Subjects: bivalve macoma-balthica; cockles cerastoderma-edule; knots calidris-canutus; mussels mytilus-edulis; oystercatchers haematopus-ostralegus; plovers pluvialis-squatarola; ragworm nereis-diversicolor; tringa-totanus l; wading bir; whimbrels numenius-phaeopus; Calidris canutus; Numenius phaeopus
• Online Access: https://research.wur.nl/en/publications/intake-rates-and-the-functional-response-in-shorebirds-charadriif; https://doi.org/10.1111/j.1469-185X.2006.tb00216.x

As field determinations take much effort, it would be useful to be able to predict easily the coefficients describing the functional response of free-living predators, the function relating food intake rate to the abundance of food organisms in the environment. As a means easily to parameterise an individual-based model of shorebird Charadriiformes populations, we attempted this for shorebirds eating macro-invertebrates. Intake rate is measured as the ash-free dry mass (AFDM) per second of active foraging; i.e. excluding time spent on digestive pauses and other activities, such as preening. The present and previous studies show that the general shape of the functional response in shorebirds eating approximately the same size of prey across the full range of prey density is a decelerating rise to a plateau, thus approximating the Holling type II ('disc equation') formulation. But field studies confirmed that the asymptote was not set by handling time, as assumed by the disc equation, because only about half the foraging time was spent in successfully or unsuccessfully attacking and handling prey, the rest being devoted to searching. A review of 30 functional responses showed that intake rate in free-living shorebirds varied independently of prey density over a wide range, with the asymptote being reached at very low prey densities (