Особенности ночевочного поведения черного стрижа (Apus apus) / The character of Common Swift (Apus apus) roosting behaviour.

Report on

Bresgunova, Olga A. (2010): Особенности ночевочного поведения черного стрижа (Apus apus) / The character of Common Swift (Apus apus) roosting behaviour. In The birds of Seversky Donets River basin 11: Proceedings of the 15th scientific conference of the Working Group on birds of the Seversky Donets River basin. Dedicated to the memory of I.A. Krivitsky (Russian). Donets: Donetsky National University Press, p. 155-160.

(APUSlist No. 3178)

by OLGA A. BRESGUNOVA

I recorded the last major Common Swift (Apus apus) flocks in Kharkov Hydropark (Kharkov River flood-plain, Kharkov City, Ukraine) after mass disappearance of Swifts from the urban quarters of Kharkov City. For this reason the study of roosting behaviour of Swifts was carried out in May-August 2005-2008 in Kharkov Hydropark (Fig. 1.). This area includes a flood plain with depression, a canal, water meadows, and forest plantations alongside the riverbed. The main vegetation types are Scots Pine (Pinus sylvestris), Russian Olive (Elaeagnus angustifolia), Ash-leaved Maple (Acer negundo), Norway Maple (A. platanoides), Black Locust (Robinia pseudoacacia), willow (Salix spp.) and Reed (Phragmites australis) (Fig. 2.). The nearest Swift nest site was located 300 m away from the floodplain feeding area, but most Swifts return to nest in an area nearly 1-1,5 km from the bed of the Kharkov River, where there are multistorey buildings. I observed the pre-roost gathering of Swifts from 30 min before sunset to darkness.

The count of Swifts continued for approximately 1,5 hour.

Google maps

Fig. 1. Kharkov Hydropark, Kharkov River flood-plain, Kharkov City, Ukraine. The circle marks the site where Swifts form a pre-roost gathering

In addition, during the period 2006-2006, I observed the roosting behaviour of Swifts near nest colonies in 5-9-storey buildings in different districts of Kharkov. Several observations were made near v. Gaydary in the Seversky Donets flood-plain (Zmievskoy District, Kharkov Region) in mid-July, 2008. The Swifts fed above the riverbed and the water meadow. Fragmentary information of roosting behaviour of what were probably the last migrant Swifts was collected in the Kuban River flood-plain (Adygea, Krasnodar Territory, Russia) in mid-August 2008, where Swifts roost on the wing above the riverbed in the multistorey building area.

Photo Olga Bresgunova

Fig. 2. Kharkov River flood-plain, Kharkov City, Ukraine

Early in May after arriving Swifts roost in cavities in buildings where they were recorded in different Kharkov districts. In this period Swifts form pre-roost gatherings in Kharkov Hydropark. Early in May I observed birds feeding together in the evening. The first Swifts appear 15 min before sunset; after sunset their number increase twofold. The birds often fly in silence. Most of them return to roost in nest holes which are remote from the floodplain feeding area and, possibly, some roost on trees. At the end of May, Swifts in the Kharkov River flood-plain demonstrate distinct behaviour. They may gather in more compact groups, fly at different speeds and produce loud screams. Most Swifts return to nest holes in the buildings but some of them roost on the wing. Swifts rise high in flocks, then they separate, remaining apart and flying silently.

In June the number of Swifts which participate in pre-roost gatherings in the Kharkov River flood-plain increases to some 300 individuals by the end of June (2006; Fig. 3.). Swifts appear in the river flood-plain 30 min after sunset. They become more active and then the Swift “swarm” flies up. This massing of about 300 individuals occurs within a restricted area of 300 m х 150 m.

Fig. 3. The formation of Swifts' pre-roost gathering in the Kharkov River flood-plain (Kharkov City, Ukraine) in the years 2005-2008.

From July pre-roost gatherings of Swifts exist in all urban Kharkov districts and in the Seversky Donets flood-plain (Kharkov Region) because juvenile Swifts leave the nest. In urban quarters near nest colonies, the first birds appear 20-25 min before sunset and the peak number is reached by sunset. The number of Swifts which participate in pre-roost flight amounts to 17-300 individuals. During the flight, the Swifts congregate together, giving chase and uttering loud screams. Then Swifts form more dense groups in the air and gain height. After that the gathering suddenly falls apart and the Swifts reduce speed. In the dark I could make out the silhouettes of solitary and silent Swifts.

In August Swifts in the Kharkov River flood-plain roost mainly on the wing and rarely in tree foliage. In mid to late August a few Swifts participate in pre-roost flight before sunset, but the majority appears at sunset. In the dark the Swifts gathering separates at once, and the birds can drop down (practically "tumble") by 1-3 individuals into deciduous and coniferous trees e.g. Scots Pine (Pinus sylvestris). Some birds prefer aerial roost. The numbers of Swifts which participate in pre-roost flight in August does not exceed 180 individuals (Fig. 3.).

The difference between the date of disappearance of Swifts from urban Kharkov quarters and Swifts’ records in the Kharkov River flood-plain is clear. Thus, in 2005 the bulk of Swifts disappeared from Kharkov on 9 August and the last individuals were recorded in Kharkov region on 17 August and 2 September (Banik et al., 2007а). In Kharkov River flood-plain I recorded 70 Swifts on 29 August (Fig. 3.) and last individuals were found here on 6 September. In 2006 the majority of Swifts disappeared from Kharkov City before 5 August (Banik et al., 2007b), but in the flood-plain I recorded flocks of 30 Swifts on 27 August (Fig. 3.). In 2007 Swifts disappeared from Kharkov City on 7 August and last individuals were seen in the Kharkov region on 26 August (Banik et al., 2009). In the Kharkov River flood-plain I recorded Swifts until 19 August (Fig. 3.). In 2008 almost all Swifts disappeared from Kharkov on 6 August, but there were pre-roost gatherings of Swifts in the Kharkov River flood-plain until 19 August. Thus, the difference between disappearance of Swifts from urban quarters of Kharkov City and records of Swift flocks in the Kharkov River flood-plain comprises 12-23 days in different years. This difference indicates that Common Swifts prefer the river flood-plain in the period of autumn migration. Probably it is typical Swift behaviour to form pre-roost gatherings at traditional sites even in the case when birds roost on the wing. It may be that the Swifts that nest in Kharkov City are replaced in the Kharkov River flood-plain by migrating Swifts.

All observations in the Kharkov River flood-plain and Krasnodar Territory (Russia) about roosting behaviour of the last single individuals on autumn migration period showed that birds sleep on the wing.

I am grateful to Jake Allsop, Cambridge for checking the English text.

References

Banik, M.V., Atemasova, T.A., Atemasov, A.A., Bresgunova, O.A., Viter, S.G., Volontsevich, A.A., Goncharov, G.L., Devyatko, T.N., Konovalenko, S.V., Kotlyar, V.I., Mironenko, I.A., Nadtochiy, A.S., Pal’val’, A.V., Yatsuk, E.A. 2007. The results of phenological observations on periodic events in bird life in Kharkov region in the year 2005. In Birds of Seversky Donets River basin 10. Proceedings of the 13-14th Meeting “Studies and protection of birds in Seversky Donets River basin”. Kharkov, p. 64-75 (in Russ.).

Banik, M.V., Atemasova, T.A., Atemasov, A.A., Bresgunova, O.A., Volontsevich, A.A., Goncharov, G.L., Mironenko, I.A., Nadtochiy, A.S., Lisnyak, S.N., Yatsuk, E.A. 2007. The results of phenological observations on periodic events in bird life in Kharkov region in the year 2006. In Birds of Seversky Donets River basin 10. Proceedings of the 13-14th Meeting “Studies and protection of birds in Seversky Donets River basin”. Kharkov, p 76-88 (in Russ.).

Banik, M.V., Atemasova, T.A., Atemasov, A.A., Bresgunova, O.A., Volontsevich, A.A., Goncharov, G.L., Devyatko, T.N., Lisnyak, S.N., Yatsuk, E.A. The results of phenological observations on periodic events in bird life in Kharkov region in the year 2007. In The birds of Seversky Donets River basin 11. Proceed. 15th scientific conference of Working Group on birds of Seversky Donets River basin dedicated to the memory of I.A. Krivitsky. Donetsky National University Press, Donetsk, p. 118-128 (in Russ.).

http://maps.google.com/