Vertical space utilization by urban birds and their relationship to electric poles and wires

Abstract

Birds living in urban areas use various human-made structures. Many artificial structures such as houses, electric poles, and electric wires are used as “perches”. The height of urban birds (vertical space utilization) may be affected by the height of these structures are. We investigated how and which height birds utilize in the urban space in Hakodate City in Hokkaido, and whether they are related to the electric poles and wires. A decision tree was constructed to analyze how differences in species (Tree Sparrow, Rock Dove, Carrion Crow, Large-billed Crow, and Slaty-backed Gull.), seasons, and in the numbers of high-rise buildings explained the observed heights of birds in the following three categories; L-zone (0–4.8 m), E-zone (4.8–14.5 m), and H-zone (all ranges higher than 14.5 m). The combination of explanatory variables that were strongly related to height differed among species. Although Carrion Crows and Tree Sparrows most frequently used heights with electric poles and wires, their usage patterns were different. For both species, the E-zone was used not only as merely a perching place but also as an important place where behaviors related to reproduction were exhibited. Knowing the vertical space utilization of birds in urban areas may help avoid future accidents involving unmanned aerial vehicles.

Appendices

Appendix 1

Weather conditions on each survey day. All routes and inter-routes were divided into three sections A, B and C. A: two parallel routes in the southwest, A: two parallel routes in the southeast, C: the rest of the north side. We surveyed a section per day. Average wind speed and deepest snow were obtained from website of Japan Meteorological Agency (https://www.data.jma.go.jp/obd/stats/etrn/select/prefecture00, accessed 28-June-2021). The traffic volume was similar between sections.

Season	Day	Section	Weather	Ave. wind speed [m/s]	Deepest snow [cm]
Wintering	2018/12/3	A	Clear	2.6	0
	2018/12/11	B	Cloudy and Sometimes snowy	2	16
	2018/12/14	C	Cloudy, with occasional snow	3.9	7
	2019/1/23	A	Cloudy and sometimes snowy	2.9	30
	2019/1/25	B	Clear, with brief light snow	2.4	40
	2019/1/30	C	Cloudy	2.3	27
	2019/2/18	A	Clear, partly cloudy	5	32
	2019/2/22	B	Clear, partly cloudy	3.2	22
	2019/2/23	C	Clear, with brief light snow	2.8	21
Breeding	2019/4/29	B	Clear	3.1	0
	2019/4/30	C	Cloudy	4.1	0
	2019/5/1	A	Cloudy	1.5	0
	2019/5/15	B	Cloudy	1.8	0
	2019/5/16	C	Cloudy	1.7	0
	2019/5/17	A	Cloudy	1.9	0
	2019/5/29	B	Clear	3.1	0
	2019/5/30	C	Clear	3.6	0
	2019/5/31	A	Cloudy	3.3	0

Appendix 2

A summary of the altitude of all 18 species observed.

Species	Scientific name	Wintering				Breeding
		Average	Max	Min	Total No.	Average	Max	Min	Total No.
Rock dove	Columba livia	14	24	0	85	11	32	0	43
Black-tailed gull	Larus crassirostris	–	–	–	0	30	43	17	2
Slaty-backed gull	Larus schistisagus	26	52	9	20	37	65	16	55
Great cormorant	Phalacrocorax carbo	–	–	–	0	–	80*	–	3
Northern Goshawk	Accipiter gentilis	–	121	–	1	–	–	–	0
Great spotted woodpecker	Dendrocopos major	–	10	–	1	–	–	–	0
Carrion crow	Corvus corone	11	62	0	62	10	39	0	40
Large-billed crow	Corvus macrorhynchos	16	62	0	71	30	97	0	36
Varied Tit	Sittiparus varius	8	12	1	7	–	–	–	0
Japanese Tit	Parus minor	7	10	7	5	12	18	7	3
Brown-eared Bulbul	Hypsipetes amaurotis	7	14	3	13	10	12	3	6
Barn Swallow	Hirundo rustica	–	–	–	0	–	46	–	2
Chestnut-cheeked starling	Agropsar philippensis	–	–	–	0	11	–	–	2
Naumann’s Thrush	Turdus naumanni	6	8	5	3	–	–	–	0
Blue Rock Thrush	Monticola solitarius	–	–	–	0	21	33	9	2
Eurasian Tree Sparrow	Passer montanus	5	16	0	208	6	22	0	273
White Wagtail	Motacilla alba	–	–	–	0	–	16	–	1
Grey-capped Greenfinch	Chloris sinica	–	–	–	0	10	17	0	20

1. *Only eye measurement