You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Factors Affecting Prey Preparation by Adult Magpies Feeding Nestlings
Adrián Ponz, José A. Gil-Delgado and Emilio Barba
Vol. 101, No. 4 (Nov., 1999), pp. 818-823
Published by: American Ornithological Society
Stable URL: http://www.jstor.org/stable/1370069
Page Count: 6
You can always find the topics here!Topics: Beetles, Magpies, Nymphs, Pica, Appendages, Adult insects, Clutch size, Food, Ingestion, Foraging
Were these topics helpful?See somethings inaccurate? Let us know!
Select the topics that are inaccurate.
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
We collected 1,138 prey items from the guts of nestling Magpies (Pica pica) using neck collars. We noted the alterations (appendages missing, breakage) shown by the prey, and gave an index of preparation to the most abundant prey types (adult beetles and grasshopper nymphs). We then related these indices to prey size, age of the nestlings, brood size, and sampling date. Fifty-seven percent of the beetles were prepared, most of them being broken. The probability of breaking a beetle increased as the difference between clutch size and brood size increased, and as the residuals of prey size on sampling date increased. The probability of having at least one elytra removed increased as the beetle size increased and as the difference between clutch size and brood size increased. The degree of preparation of beetles decreased as their size decreased, as the nestlings grew older, and as the difference between clutch size and brood size decreased. Seventy-one percent of the grasshopper nymphs were prepared, the degree of preparation decreasing as their size decreased and as the season progressed. We conclude that the degree of prey preparation by Magpies feeding nestlings is the result of a trade-off between the benefits obtained by the nestlings and the costs to the parents.
The Condor © 1999 Cooper Ornithological Society