Australian Falcons by Stephen Debus

Author:Stephen Debus
Language: eng
Format: epub, pdf
ISBN: 9781486315789
Publisher: CSIRO Publishing
Published: 2022-07-27T00:00:00+00:00

Social behaviour

Well known, with much new information supplementing HANZAB, although no studies of marked birds. Recent studies by Debus et al. (2005), Debus and Tsang (2011), Debus and Zuccon (2013), Charley et al. (2014), Whelan et al. (2016) and Debus et al. (2017a,b). Black Falcons breeding in farmland, within sight of farmhouses, are rather confiding and tolerant of familiar, routine human (e.g. farming) activities to within 50–100 m of the nest, but pairs nesting in more secluded woodland may be warier and flush more readily at human approach (Debus et al. 2017b). Although the Black Falcon is usually seen singly, in pairs or (in the post-fledging period) in family groups of adult(s) and dependent juveniles, several or many non-breeding individuals (up to 14) gather at grass or stubble fires or agricultural activities that flush out prey (Debus and Zuccon 2013; Whelan et al. 2016). Single individuals sometimes soar with a flock of Black Kites (Fisher 2009; S. Debus), among which they may be overlooked by observers and perhaps by prey species. Black Falcons are sometimes aggressive towards larger non-raptorial birds (Bartram 2012; Whelan et al. 2016). In central Australia, Black Falcon sightings were distributed throughout the day; they were observed perching in dead shrubs and live trees, and flying low (< 20 m above vegetation) or moderately high (20–50 above the vegetation) (Aumann 2001).

Comfort behaviour. Brooding females sometimes sun-bask on an exposed perch near the nest, facing the rising sun with belly feathers fluffed, on cold mornings (Debus et al. 2005).

Aerial activity. In the pre-laying phase, members of a breeding pair soar together or alone and sometimes perform manoeuvres around or over the nest, some of which may be territorial rather than courtship displays. These manoeuvres include aerobatics (mock attack and defence, ‘following’ flights, figure-of-eight flights, V-dives), ‘high winnowing’ flight above the plane of the body while soaring with a slight dihedral, and laboured flight with canting from side to side (‘undulatory roll’) (Debus et al. 2005; Debus and Tsang 2011; Whelan 2013c; Charley et al. 2014; Whelan et al. 2016; Debus et al. 2017b).

Agonistic behaviour. Breeding Black Falcons direct the above stereotyped displays (high winnowing with dihedral, V-dives, undulatory roll) at intruding conspecifics and, if intrusion persists, they chase, stoop at and sometimes grapple with the intruder (Charley et al. 2014; Debus et al. 2017b). Breeding pairs defend territory boundaries against neighbouring pairs by aerial skirmish (Schoeb et al. 2019). Breeding Black Falcons strongly defend the nest against other bird species, notably corvids and other raptors. Depending on the level of threat (intruder species and its height or proximity), breeding Black Falcons direct the high winnowing display, with cackling, at other raptors, or attack intruders by chasing, stooping and cackling, particularly at corvids in the pre-laying phase and large eagles in the nestling period, although defence against small or medium-sized raptors can be mild and inconsistent (Newman and Lindsey 2007; Debus and Zuccon 2013; Charley et al. 2014; Whelan et al. 2016; Debus et al. 2017b; Schoeb et al. 2019).

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