Low temperatures affect the photoperiodically induced LH and testicular cycles differently in closely related species of tits (Parus spp.).

Photosensitive great tits (Parus major) and willow tits (P. montanus) were exposed to long days (20L:4D) under three different temperature conditions (4+, +10, and +20 degrees C) in early winter. The two species showed significant differences in their LH and testicular reaction patterns to low temperatures.

Hormonal correlates of migration and territorial behavior in juvenile willow tits during autumn.

This study compared plasma levels of dihydrotestosterone, testosterone, corticosterone, luteinizing hormone, growth hormone, and prolactin in migrating juvenile willow tits with those in territorial juveniles. Both categories of birds were caught in late September. Migrating juveniles had higher plasma levels of corticosterone than territorial juveniles.

Seasonal changes in body weight, fat depots, and plasma levels of thyroxine and growth hormone in free-living great tits (Parus major) and willow tits (P. montanus).

Annual changes in body weight, fat depots, and plasma levels of thyroxine (T4) and growth hormone (GH) were studied in free-living great tits and willow tits. Birds were collected during six ecologically well-defined periods of the year. Special attention was given to the nonreproductive part of the year.

Plasma levels of luteinizing hormone and steroid hormones in free-living winter groups of willow tits (Parus montanus).

Plasma levels of LH, DHT, testosterone, and corticosterone were measured for all members in free-living winter flocks of willow tits, Parus montanus. Hormonal data were related to (1) flock size and (2) age/sex differences. The winter flock defends a large winter territory and shows a well-established social hierarchy in which adults consistently dominate first-year birds.