Finding Ayres's Hawk-Eagle

Eagle over Karatu: photo Martin GoodeyAyres's Hawk-Eagle (Aquila ayresii) is essentially a forest bird and, although widespread on the continent of Africa, is "inexplicably scarce and local", and thus can be one of those toughest of birds to see. It is hard to guarantee that any visiting birder 'will get to grips with' this most lovely raptor, even on a three week safari into the wildlife treasure trove of northern Tanzania.

By way of contrast it should not take too long for the keen birder to find both African Hawk-Eagles (Aquila spilogaster) and, in the proper boreal season, 'wintering' Booted Eagles (Aquila pennatus); yet neither species, close cousins of Ayres, is what one could call a common bird.

In the photographs, particularly in the composite picture below of first year Booted and Ayres's (Hawk-Eagles), one can discern the fairly subtle structural as well as plumage differences. Especially the more compact form of Ayres's; it has more a 'muscular chest', proportionately shorter, slightly wider wings (formed by a broader 'arm' and fuller 'hand') and the very slightly longer, more closely and finely barred tail of young Ayres's when compared with a Booted of the same age. The more compact physique of "Ayres" being a perfect adaptation for hunting through the tangled confines of an evergreen forest canopy - or for that matter in narrow urban alley ways!

First years of Booted Eagle and Ayres Hawk-Eagle: Note the subtle structural as well as plumage differences; especially the more compact body, proportionately shorter, broader wings and slightly longer, more closely barred tail of Ayres, perfect adaptations for hunting through the tree canopy of woodland

CORRECTION: I now believe both birds in this picture are Booted Eagles, see UPDATE and discussion in the comments section below.

Thomas Ayres (1828 - 1918) shot the type specimen of Spizaetus ayresii (Gurney) in Kwa-Zulu Natal, South Africa, probably around what is now Pinetown, in 1862. Over one hundred years later the late Leslie Brown, that greatest of East African raptor 'fundis', was wondering why Ayres's Hawk-Eagle, an eagle which evidently feeds upon a wide range of smaller birds, remained such a rarity. In Volume One of The Birds of Africa, the definitive African Handbook which he initiated and upon which he was lead author until his untimely death, Leslie Brown described Ayres's eagle thus:

"Little known outside the breeding season... seldom seen, usually suddenly, flying briefly near forest, over dense woodland along rivers, or on isolated mountain tops... often appears in swift descending flight as if from nowhere... appears to spend hours perched within the canopy of large leafy trees and is then very inconspicuous. An extremely dashing swift little eagle, with magnificent flying powers, combining the speed of large falcon with the agility of goshawk, hunts prey in swift, near-vertical dives, with wing-tips folded to tail-tip in characteristic heart-shaped silhouette, shooting into forest canopy and weaving at speed in and out among branches. Can dive into forest canopy at great speed emerging with prey without stopping, in manner unique to this species. Probably catches many birds in flight."

Ayres's Hawk-Eagle has always been, no doubt, a raptor of partly open or patchy evergreen forest and 'forest islands' and is therefore found primarily in hilly terrain; especially it seems where these abutt the lower edge of thicker evergreen forest in more mountainous districts. This habitat requirement of - 'evergreen forest edge' explains why the vast majority of my sightings of Ayres's Hawk-Eagle here in northern Tanzania come from just two, relatively small areas, where our respective life-style journeys - bird and man - most frequently intersect.

Firstly my local patch i.e. the lower slopes of Meru on the northern edge of Arusha town; and secondly the lower edge of the Ngorongoro Conservation Area along the boundary of the semi-evergreen forest of the eastern Crater Highlands, just above Karatu town.

Nowadays although "Ayres", as in Aigle d'Ayres, as one must prefer to call it, is known to occur in well-developed broad-leaved woodland, on heavily wooded hillsides, and even in eucalyptus plantations in what has been called 'African rural suburbia'. It is believed to be everywhere "sparse and uncommon". Whilst it is present all year in many regions of Africa, some populations, especially in the south, are believed to be, at least in part, migratory.

Ayres1: Martin GoodeyAyres2: Martin GoodeyAyres3: Martin GoodeyFemale Ayres Hawk-Eagle: Anabel HarriesThe pictures to the left show adult Ayres's Hawk-Eagle; the first three is probably of a relatively young male who is therefore only lightly spotted on the breast and flanks. Photos taken above Gibb's Farm Karatu, in March 2007 by Martin Goodey.

The fourth picture shows a heavily marked adult female Ayres's Hawk-Eagle photographed near Arusha in 2006 by Anabel Harries; note that some adults when seen from below reveal small pale windows in the primaries

Breeding activity in eastern and southern Africa is initiated during the early cool months, the single egg being laid typically from May onwards into July. Thus the greatest demand for food by the growing youngster occurs during the period August - November. In upland East Africa this certainly does not coincide with the peak abundance of prey in forest areas; chiefly smaller birds - perhaps mostly doves and passerines. However Brown and Britton have speculated that reduced leaf cover might make these birds a lot easier to catch at this season than they are at other times of the year.

Leslie Brown, based on his own detailed observations over many years in Kenya, suggested that Ayres's Hawk-Eagle is a very conservative bird; what they used to call "a shy breeder". They select thickly-foliaged trees in rugged terrian and he showed that it probably suffers as a species from very low productivity. One faithful pair produced eggs only three times in a twelve year period. Furthermore he showed that they tend to be extremely faithful to their chosen nest site, preferring to use the very same nest, in the same tree, year after year despite deleterious changes to that nest, to the tree, and to the habitat round about. Such constraints, even when operating alone, would account for this bird's rarity.

Outside the breeding season it leads a solitary existence and will occupy a greater variety of habitats; such as the eucalyptus plantations of semi-urban areas in the south east of the continent. At least this has been shown to be the case in cities such as Harare and Bulawayo in Zimbabwe. In these areas each bird appears to establish and to defend a non-breeding territory. As Stuart Irwin recorded in his excellent study of the Birds of Zimbabwe, one individual appeared in the same residential district of Bulawayo each year, arriving sometime between late October and early November, and stayed there for up to five months. During its stay this bird would become decidedly tame, for the entire duration of the wet season in eight consecutive years, until some fallen character decided to shoot it! Three different Ayres were recorded 'wintering' in this same district of Bulawayo during those eight years.

Such an agile and rapacious bird, an Ayres's Hawk-Eagle, once seen and recognized can be but rarely forgotten. It is always an uplifting and for me a serendipitous experience to find, or perhaps to be found by, one of these "plucky little eagles". So far as I am aware most meetings with Ayres's are more than memorable; some are positively thrilling, one encounter last year was almost frightening.

In the very centre of Arusha, on Boma Road, there's a coffee shop-cum-restaurant known to all as Jambos. It's frequented by guide-book travellers with time on their hands and those residents in need of some down-town diurnal refreshment. One afternoon late last September whilst taking a cup of cha with some conservation-colleagues in a dingy back room there I inexplicably felt the need to go outside and buy some fresh papaya from some barrow-vendors in an alley round the corner. As I walked out westwards into the afternoon glare I noticed what at first glance was assumed to be just a street-wise Yellow-billed Kite (Milvus parasitus) circling the Arusha Hotel, at the end of Boma road. And so, with a green papaya looming in my mind's eye, I turned the corner.

Some five paces later, I heard simultaneously the wild loud "teee-oo" whistles, and felt the dark and rushing, frenzied forms of Red-winged Starlings, black arrows pelting earthwards from second storey rooftops all around. And then a tightly-bunched flock of about a dozen Speckled Pigeons (Columba guinea), softly oblivious in their maroons, and pinks and grey; who had been pecking at spilled grain in that alley out the back, simply exploded "Boompf-plap-plap-plap!" The flock scattering across the pavement in front of and all around me. Intuitively my shoulders hunched, and my face flinched upward, eyes squinting into the bright sun. An incoming heart-shaped 'rocket-propelled' projectile, in an instant was passed me, a feathered streaking blurr, all blotches black-and-white; the heart-stopping apparition of - a stooping adult Ayres. Up and over the grey corrugated roof .. and .. gone. Leaving me to hover alone in the shared history of that priceless birder's moment.

I think that he missed us all that time. Though I bet it's taking me somewhat longer than those 'peace-loving' pigeons to recall that loss of self!

Adult African Hawk-Eagle and Wahlbergs Eagle: Kleins Camp, Martin Goodey

Birdman of Arusha on August 3, 2007

Photos by Martin Goodey

UPDATE from an email discussion:

Dick Forsman wrote:

Hi James,
I hope this mail reaches you OK, it is a reply to your last mails to
have reached me.

I had a good look at your Karatu bird and got an opinion, but first let
me tell you about my experience with Ayre's. I have seen in all ca 20
different Ayre's over the last 10 years, both adults and juveniles. Most
of them are from Ethiopia, but several also from The Gambia, where it
was thought to be a rare bird, and a few from Kenya. In the field I have
never experienced it to be difficult to id., although some of the views
have been pretty distant. It has clearly a different silhouette from
Booted, with shorter and relatively broader, more rectangular wings and
the underwing barring is always distinct and obvious compared to the
underwing of Booted. The hunting behaviour of the two is very similar
in my view, with both birds hanging motionless against the wind, often
very high up in the air, stooping like Peregrines to disappear into the
canopy.

I believe your Karatu bird is an immature Booted. The misleading
characters are the barred underwing and the pale head, but to me both
are photographic artefacts, enhanced in the image. The underwing barring
does exist in Booted, and get's more pronounced during winter as the
plumage fades, compared to fresh autumn birds in Europe. However, the
underwing barring is not contrasting enough for an Ayre's and the head,
although appearing very pale, is actually faded brownish with a distinct
Booted-look to it, when you look carefully. Pale juv Ayre's often have a
truly white head, but with dark goggles, not unlike juv Honey-buzzard
(or juv Martial) in similarly pale plumage. This is something you never
see in Booted, which always feature a standard head. Another character
of interest is the line of dark spots to the greater underwing coverts,
in my opinion a diagnostic Booted feature and something I cannot recall
having seen in Ayre's (but this is from the top of my head- I have not
checked my photos yet). And, Booteds actually have barred tails, but in
juvs the outermost pair of tail-feathers is unbarred, so when the tail
is folded it appears uniform.

 

 

Martin Goodey sent more pictures of the same bird.

Please find attached 4 of 12 images of the Karatu Eagle.
These are as they came out of the camera. I have only converted them from RAW to Tiff then cropped the full size image, no re-sizing or re-positioning. There has been no sharpening or level adjustment applied, play around with that if you wish. Finally the images were "saved to web" as jpegs so some loss of quality may occur.

I have enjoyed following the debate on this "highly instructive bird"

 

Bill Clark commented on those pictures:

It is obvious from these nice pics that the eagle in question is a juvenile Booted Eagle, and not a Wahlberg's Eagle as I had thought from the two thumbnail pics. The definitive field marks are the white uppertail coverts and the manner of how the wings are bowed, neither of which were evident to me in the original photos. I can see clearly now the dusky face and lack of banding on the outer tail feathers.

 

Rob Davies commented and sent pictures of an Ayre's in Ghana

Thanks for the interesting discussion and thought-provoking photos – nice website – makes me homesick for Africa

As Bill says my vote is for Booted. Something that I really notice on Booteds is the clear black dots on the greater underwing coverts especially out on the hands.

James you asked for photos of imma Ayres

Attached is a series I took of a bird I believe to be an immature pale Ayres taken at Shaii Hills in Ghana

It took a while to work out what it was despite very clear views but eventually we agreed on Ayres (David Allan Morne Du Plessis and some other good birders present). I think Ayres are always more hawkie and more barred. This bird does seem to have dark markings on the underwing coverts but with barring and not isolated against the pure cream as seems to be the case for Booteds

Hope it helps the debate

Ayres from Ghana 1: photo Rob DaviesAyres from Ghana 2: photo Rob DaviesAyres from Ghana 3: photo Rob Davies

My hunch is that it is a pale (bleached?) juvenile with the first dark streaks of an adult or subadult coming through

Ron Hartley would have been the best person to advise on time to maturity – sadly no longer with us

I would expect small eagles to reach maturity quicker than the big eagles which take 3-5 years

next