The Great Tit is a widespread species. The birds’ relationship with the territory varies – from sedentism, nomadism and local movements to regular seasonal mid-distance migrations. Scientists suppose the species’ expansion to the north of Fennoscandia is associated with growing urbanization: colonizing high latitudes, the birds choose built-up areas and stay in or near human settlements during the wintering and breeding periods.
The effect of urbanization of the Great Tit has been studied actively in the past few decades, but the age structure of the breeding population is rarely analyzed. Meanwhile, this is one of the key local population characteristics indicative of the level of mortality, quality of the habitat and other features of the birds’ ecology. The study of Karelian scientists bridges this gap. In this effort, ornithologists compared the breeding populations of the Great Tit in localities situated at different distances from the wintering grounds.
The study was carried out in 2015–2021 in two localities: at the Institute of Biology KarRC RAS research station on Lake Ladoga coast and not far from Lake Onego, in the Petrozavodsk University Botanical Garden. Artificial nests have been built for the birds in both localities. Scientists annually monitored the use of the nests and labeled almost all the chicks.
As a result, they found significant differences in the shares of young birds in the breeding populations. To wit, the prevalent share in boreal forests on Ladoga coast belonged to yearlings (59 %), while their share in the Botanical Garden and its surrounding forests was much lower (28 %) and older birds prevailed there. The relationship with the territory in Great Tits varied also in terms of philopatry, i.e., the tendency to remain in or regularly return to a certain area. As opposed to the inhabitants of Petrozavodsk suburbs (Botanical Garden), birds at the Mayachino Research Station (Ladoga area) show rather low fidelity to their former breeding grounds.
Scientists attribute the differences in the age structure of birds in the two localities to their different territorial behavior strategies. A majority of migratory great tits are young birds, while most adults are either sedentary or migrate over short distances.
Great Tit nests can be seen in the city, too: in nest boxes, tree hollows, or even cavities in light poles. The birds have two breeding cycles: in May to early June and in late June to early July. Scientists remind: brooding birds must not be disturbed.
“When in stress, tits often abandon their nests. They can be affected by noise or intense activity near the nest. We have previously studied their breeding in different areas of the Botanical Garden: the recreational area, where people walk around a lot and noisy operations may take place, and in the “reserve” area of forest with native flora. The breeding success of tits in the latter is much higher”, – ornithologist Andrey Tolstoguzov tells.
Spotting a nestling fallen out, one can try to return it to the nest, which is likely on the tree under which it’s sitting. Fallen-out nestlings must not however be confused with fledglings. While the former are partly bare or covered in down, fledglings are feathered chicks that can see well and are sturdy on their feet but are only learning to fly.
“Parents provide them with supplementary feeding while they learn to fly. Do not pick up fledglings – they’re not abandoned. If you fear the baby bird may get killed by a cat or dog, you can lift it to a shrub or a tree branch, but never take it away home. The parents will keep looking for their fledgling for a day a half or two”, – Andrey Tolstoguzov added.
Photos by Tatyana Yanchenko
