Comparative ontogeny of behaviour in several Passerines: A tentative study

Abstract

The comparative study of the ontogeny of behaviour should be of evolutionary interest, as in the morphological characters. Here some reported data of observations of this sort are extracted for comparison from the works of Barrand (Great Tit, Chaffinch), Blase (Red-backed Shrike), Kuroda (Grey Starling), Messmer (European Blackbird. Original was not available) and Sauer (Garden Warbler).
Twenty four behaviour items classified into sight development, physical behaviours (preening, etc.), self protection (crouching, fleeing, etc.), social behaviours (aggressiveness, juvenile song, juvenile nesting, etc.) and food getting (oriented gaping, pecking, species-specific use of bill, self foraging and drinking, etc.) were selected for comparison.
It could tentatively be concluded that: 1. The duration from hatching to self foraging does not differ much by species with different habits and duration of nestling life. This should there-fore be the evolutionary basic Passerine character. 2. The hole and open nesters would have developed later adaptively. The nestling life was lengthened in the hole nesters (about 20 days) and shortened in the open nesters (10-15 days) as the result of natural selection against predators, but the basic growth pace was not changed. Thus hole nest chicks that stay longer in the nest are fed by parents shorter time after flying since they are well grown and open nest chicks fly precociously and are fed longer (Thus they retain incomplete adaptation against the danger of predation when flying). 3. This difference of the nestling period caused the difference in the timing of physiological and behavioural growth of early nestling life, such as eye-opening, lateral sight, preening and self protection, etc. These were accerelated in open nest chicks so as they have developed by the time of their precocious flying from the nest. 4. But, this accerelation of the occurrence of behaviours seems to have not influenced the basic timing of the final completion of self foraging. However, at the time when self foraging becomes established species-specific use of the bill (and feet) occurs similarly at around 20-25 days after hatching irrespective of the difference of habit by species. 5. The social habits occur first as an aggressiveness against each other (head forward posture, maintenance of individual distance) at different period by species (this occurs early at about 20 days in strongly territorial species), but always after or when the self foraging is established. 6. These species-specific behaviours (4 and 5) which occur latest during the ontogeny should be the ethological characters which have evolved recently.