Nom du corpus

Corpus Systématique Animale

Titre du document

Siblicide, parent-offspring conflict, and unequal parental investment by egrets and herons

Lien vers le document
Springer (journals)
Langue(s) du document
Type de document
Nom du fichier dans la ressource
  • Douglas W. Mock
  • Department of Zoology, University of Oklahoma, 73019, Norman, OK, USA

O'Connor (1978) generated behavioral predictions from Trivers's (1974) theory of parent-offspring conflict (POC) in relation to avian brood reduction, especially for species using escalated sibling aggression. In general, when daily mortality rates fall between certain values (the “mortality difference thresholds” for parents and surviving offspring: O'Connor 1978), POC is expected. At such times parents and the early-hatching “senior” offspring are expected to disagree on the necessity, or at least timing, of the “victim” chick's death. Because that death is promoted directly by the senior chicks and because parents have realistic means of nullifying those efforts, behavioral conflict is expected. I examined the activities of all family members in one siblicidal (great egrets, Casmerodius albus) and one nonsiblicidal brood-reducing species (great blue herons, Ardea herodias) of ardeidae in Texas nesting colonies. Daily mortality rates over two breeding seasons approximated the predicted POC zone for four-chick (“B/4”) heron broods and three-chick (B/3) egret broods. As predicted, egret sibling aggression was significantly lower in two-chick broods. Herons seldom fought, regardless of brood size. Special attention was paid to the egret B/3 data for behavioral manifestations of POC. Parents did not interfere overtly with sibling fights (99.2% of 2,829), but parents seemed to have a subtle mollifying effect on the aggression (fewer “sever” fights occurred when parents were present). Parents showed no favoritism in food distribution to dying victim chicks. The mixed results are consistent with two rather different POC interpretations: (1) that significant conflict exists and the offspring are “winning” or (2) that there is no significant evolutionary conflict. In the latter case, parents are regarded as creating asymmetries among offspring (e.g., via hatch asynchrony), then leaving competition among siblings to run its course without further intervention (“laissezfaire” policy). This view explicitly recognizes that siblicide and other investment-skewing selfish chick behaviors may serve parental interests well-i.e., that equal allocation of resources is not likely to be the parental optimum. Using the relative reproductive values of each nestling as an index of the parent's unequal parental investment optimum produces a closer fit to the observed food distribution skew, but does not resolve the question of whether conflict remains.

Catégories Science-Metrix
  • 1 - health sciences
  • 2 - psychology & cognitive sciences
  • 3 - behavioral science & comparative psychology
Catégories INIST
  • 1 - sciences appliquees, technologies et medecines
  • 2 - sciences biologiques et medicales
  • 3 - sciences biologiques fondamentales et appliquees. psychologie
  • 4 - ecologie animale, vegetale et microbienne
Catégories Scopus
  • 1 - Life Sciences ; 2 - Agricultural and Biological Sciences ; 3 - Animal Science and Zoology
  • 1 - Life Sciences ; 2 - Agricultural and Biological Sciences ; 3 - Ecology, Evolution, Behavior and Systematics
Catégories WoS
  • 1 - science ; 2 - zoology
  • 1 - science ; 2 - ecology
  • 1 - science ; 2 - behavioral sciences
Identifiant ISTEX

Behavioral Ecology and Sociobiology

Année de publication
Présence de XML structuré
Version PDF
Score qualité du texte
  • Oiseaux
Type de publication
Powered by Lodex 9.3.8