Observations on the breeding biology of Long-tailed Tits

Abstract

1. Observations were made on 48 pairs, 71 nests of Aegithalos caudatus trivirgatus in Nagano, Honshiu, during the breeding seasons 1951-1961.2. Sexes were identified by behaviour, difference in curved and worn tail feathers and leg bands.3. Breeding is commenced in accordance with budding season of trees. Some begin nesting as early as in February but their nesting periods are prolonged owing to occasional cold spells than in late breeders.4. Pair formation precedes the nest-site selection. Pair-groups are formed by local adherance within an winter flocking area. Even after nesting is commenced, pair-groups may be re-formed by cold spell.5. Nests are placed in wood-edges and canopies, and the twigs, more than 10m in height, of evergreen needle-leaved trees are most often selected. In desiduous broad-leaved trees the nest is found 3-10m from the ground and in bushes below 3m.6. If nest is destroyed during beeding season it is renested, but towards the end of the season not.7. Both sexes work for nesting and total activity time is a little less than resting time. Nesting period may be as long as 2 months for some early nesters, but only about 10 days for later breeders.8. They roost in a bush in early nesting period but after nest-wall is completed they use it for roost.9. The ratio of time, non-attendance/incubation time, is nearly 1 in early nesting period and almost 2 later.10. Roosting in nest is first led by male but the female enters first followed by him with a certain behaviour pattern.11. When chicks hatched, male passes food to the female who feeds but ofter a few days both parnets feed the chicks directly.12. A parent fed the chick average 0.33 times per minute but a little less in early and later period.13. Male may lead the female for feeding but the latter feeds first, during which the male makes display behaviour and then feeds the chicks.14. The up-right flight display chiefly made by the male is performed at certain places during nesting seasen aod becomes restricted to the neighbourhood of the nest during egg-laying through incubation and feeding periods. Soon after the hatching this behaiour is at its peak.15. The territory is indistinct and only the nest is defended. The display behaviour is not used for defence of territory.