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Medientyp:
E-Artikel
Titel:
Brood Reduction in the Chihuahuan Raven: An Experimental Study
Beteiligte:
Haydock, Joseph;
Ligon, J. David
Erschienen:
The Ecological Society of America, 1986
Erschienen in:Ecology
Sprache:
Englisch
ISSN:
0012-9658;
1939-9170
Entstehung:
Anmerkungen:
Beschreibung:
<p>Hypotheses concerning the adaptive significance of asynchronous hatching in relation to brood reduction were tested by manipulating broods of Chihuahuan Ravens (Corvus cryptoleucus) in southeastern New Mexico in 1981 and 1982. Breeding success was also monitored at the study site in 1978 and 1979. Manipulations included: (1) exchange of nestlings between nests to obtain nests with five or six nestlings of nearly equal size, (2) transfer of the largest nestling from one nest to another where it was approximately equal in mass to the smallest nestling, and (3) transfer of the smallest nestling from one nest to another nest where it was approximately equal in mass to the largest nestling. In control nests, the most productive clutch size was larger than the most common clutch size. Growth rates and masses for nestlings that fledged were similar in most cases, regardless of clutch size or hatch position. Fledging success was significantly higher in the experimental broods with equal-sized nestlings than in the control nests in which six young hatched in 1981. However, in 1982, fledging success was nearly equal in the experimental and control nests. Although growth rates were not significant lower, fledgling masses were significantly lower in the experimental broods with equal-sized nestlings. Smallest nestlings transferred to a largest nestling position in another nest fledged as well as the largest nestlings in control nests. Largest nestlings transferred to a smallest nestling position fledged as rarely as smallest nestlings in control nests. Lack's hypothesis that asynchronous hatching allows for adjustment of brood size is supported. However, our limited experimental data suggest that more young often could be fledged if hatching wee more synchronous.</p>