Following the first part (on data of April 13-30), this second part describes the observation data of May 4-18, 1969 on the parental behavior of a breeding pair of
Corvus macrorhynchos in middle nesting period (16-30 days after hatching).
1) The daily life of the pair was the same in general pattern as in earlier nestling period (cf. first part), but the amount of each feed for chicks carried in parents' buccal sac seemed to have increased judging foom larger swollen throat of parents.
2) With the growth of chicks, the female occasionally spent rather long time (more than 30 minutes) off the nest for her own feeding or excercise flying to some distant buildings, during which the male rests and watches at high top of a building. After along off, the female fed the chicks a few times with short intervals.
3) The female's defence drive increased with the growth of chicks. She became aggressive even against small birds such as the bulbul
Hypsipetes amaurotis which may fly into her nesting gingko tree and she was observed to straightly fly back from distant building to that gingko tree which a bulbul flew in. She also at once chased away a
Psittacula parakeet (an escaped cage bird) which happened to fly into that gingko tree.
4) As mentioned in the first part, the female was usually the more aggressive than the male against trespassing other crows, but when she was out for own feeding, etc., the male was seen to chase the intruder.
5) Parent birds are very nervous in this period (May 13, 14, 25 and 26 days after hatching) for protection of chicks. They continuously uttered warning 'ga, ga' note at lower branches of the nesting tree against a cat on the ground. Against approaching observer, the female came down to overhead branch, with the same 'ga' note, vigorously pecking at perch, breaking down twigs and snatching leaves which she may grasp with one foot (see photo 2 and photos in Misc. Rep. Yam. Inst. no. 41). These are displacement threat actions released against strong enemy. The male, however, only watched her from up on high branch, with continuous 'ga' notes.
6) As the chicks grow from 16 (May 4) to 30 (May 18) days after hatching, the female's off-nest time increased from 0.5-32 (av. 11.4) minutes to 6-41 (av. 19.6) minutes with the decrease in on-nest time from 1-15 (av. 8.0) minutes to 1-5 (av. 1.8) minutes; thus with the decrease of brooding rate from 41.31% to 8.80%.
7) The feeding frequency and interval varied by date and time of day and were more variable in the male, but rather constant at more or less about 14 minutes intervals or 4 times per hour when feedings by male and female are totalized (These will be analysed in later report).
8) From 17 days after hatching the parents took, after feeding, chick's feces which they stored in the buccal sac to drop from the branch of nearby tree, but this was not frequent during the observation period. In one occasion, the female didn't drop the feces and probably ate it.
9) Toward middle nestling period, female didn't remain long in the nest after feeding the chicks and thus the male and female often returned to nest in turn for feeding of chicks. If the male came back, with food in throat, and the female was still in the nest, he waited until she gets out of the nest (not passing food to her as in incubation (or brooding) period) (But, rarely he came to nest and female flew out). The female, on the other hand, would come into the nest although the male was there, and the male at once flew out of the nest (But, once the female was observed to wait until the male came out of the nest). Thus, the male and female do not feed the chicks together and the female is behaviorally slightly dominant in feeding. The female usually stayed a few minutes in the nest after feeding, but the male's feeding ended in a minute.
View full abstract