HOW THE MALE BIRD DISCOVERS THE NESTLINGS: Continued from ‘Ibis' 95: 37
Authors: Skutch Alexander F. 
Published: April 2008

Summary

The species concerned chiefly in this study are those in which the male does not incubate. Among such species the male may show interest in the nest while it contains eggs by: standing guard, bringing food, bringing materials of which the nest is constructed, escorting the female on her return to the eggs, and periodic visits of inspection. These contacts, which an individual male may use singly or in combination, are important in preparing him for the discovery of the nestlings.
Standing guard is most common among big, powerful birds, such as jays. Among weaker birds it seems to be chiefly individual rather than specific.
Three types of food‐bringing are distinguished: (1) sustaining, when the male provides most or all of the food for his incubating partner, as in hombills and goldfinches; (2) occasional, when scattered feedings do not materially diminish the time the female must devote to hunting her own nourishment; and (3) anticipatory, when the male brings food for his unhatched offspring rather than for his mate. Rarely a female bird offers food to her unhatched eggs.
Details of the events leading up to and following the male parent's discovery of the nestlings are given for 18 nests of 14 species in 7 families, together with less complete observations for several additional nests. Most of these studies were made in Costa Rim.
Eight male parents brought food within an hour after the first egg hatched; eight in from one to six hours; five in from six hours to 1 1/2 days; one between the sixth and tenth day after hatching.
In no instance did the female parent successfully attempt, by voice or gesture, to inform her mate that the eggs had hatched. At most she could demonstrate to him her own increased need of food. The male was obliged to discover the nestlings for himself; and his promptness in doing so depended as a rule upon the habits he had formed while his mate incubated (see para. 1 above).
If the male had not brought food during the period of incubation, he did not (in the cases adequately studied) come with a morsel until after he had seen the nestlings, the sight of which stimulated this new activity. If he had been bringing food before the eggs hatched he might have a morsel in his bill when he first saw the nestlings, and feed them at once. Among birds of this group it seems likely that the male was in some instances led to carry food to the nest by seeing his mate do so.
Male birds which do not incubate are often impatient to begin feeding. They may bring food and offer it to the unhatched eggs, or attend the nestlings in a neighbouring nest of another species until their own eggs hatch. When they first become aware of their own nestlings they may bring far more food than is needed, and present it again and again to the satiated babies. The female often benefits by this excess food, and may sit more constantly than before the eggs hatched.
In periods of inclement weather, and especially with large broods, prompt feeding by the male may be essential to the survival of the nestlings. In mild weather, and with small broods, his promptness seems tess important.