Parental Feeding in a Male Great-Tailed Grackle

Abstract

In the Common Grackle (Quiscalus quiscula) and other monogamous species of grackles of the genus Quiscalus, males feed the young as regularly as do the females, but males of the promiscuous Greattailed Grackle (Quiscalus mexicanus) and Boat-tailed Grackle (Q. major) normally take no part in parental care of the young (Selander and Giller, Condor 63:55, 1961; Skutch, Pacific Coast Avifauna 31:328, 1954). Therefore, the following account of an adult male feeding fledglings is noteworthy. On 29 July 1967 in Austin I saw an adult male walking across a lawn, followed closely by two juveniles, which were directing begging displays to him. This in itself was not novel, since hungry juveniles, especially when newly fledged, occasionally direct begging displays to males. However, as I approached the trio, the adult male, rather than flying away as I expected, became alert and wary, gave chut warning calls, and remained with the juveniles, thus exhibiting behavior that is typical of a female with fledglings. Backing off, I continued to watch the birds, and soon the juveniles starting begging again. The male picked an insect from the grass and fed one juvenile, foraged a moment, caught another insect, and fed the other juvenile. Shortly thereafter the male flew off, followed closely by the two juveniles. This observation of parental feeding by a male Quiscalus mexicanus supplies another bit of evidence supporting the generalization, derived from studies of birds and other vertebrates, that behavior normally manifested only by the female is latent in the male and may be expressed under an appropriate set of internal and external stimulus conditions. In view of the importance of gonadal suppression in the facilitation of parental behavior in birds (see review by Eisner, Anim. Behav. 8:171, 1960), it is perhaps significant that the young birds involved had fledged unusually late in the season, when the male had, in all probability, completed gonadal regression and was in a phase of the annual cycle in which testosterone production by the testes is minimal (Selander and Hauser, Condor 67:165, 1965). Hence, as far as hormone titers are concerned, the internal state of the adult male may have been similar to that of a female in the post-incubation period of the annual cycle.