Black-eared Cuckoo

A Black-eared Cuckoo has black ear coverts

Following a discussion on the Canberra Ornithologists' Group chatline on the identification of a young Horsfield's Bronze-Cuckoo Chrysococcyx basalis versus a Black-eared Cuckoo Chrysococcyx osculans, I would like to add a few pointers to the plumage differences as described in HANZAB (Handbook of Australian, New Zealand and Antarctic Birds). Unfortunately, I do not have an image of a young Horsfield's Bronze-cuckoo but I refer the reader to the photograph taken by Kym Bradley which opened the discussion on what species and age the bird was that she had photographed. To see the photograph click here to open the page in a new tab for comparison with the photographs taken by me of Black-eared Cuckoos below.

The following text is an abbreviated interpretation of the description on pages 705/6 of HANZAB vol. 4, and I have attached photographs to illustrate the features mentioned, adding further points of note where these are illustrated. The list of pointers described to differentiate between Black-eared Cuckoo (BEC) in all plumages and juvenile Horsfield's Bronze-Cuckoo (HBC) are as numbered in HANZAB.

A Black-eared Cuckoo in 1st year plumage
 - superficially similar to the young Horsfield's Bronze-Cuckoo photographed by Kym Bradley

(1) The BEC is much paler with more uniform upperparts and no conspicuous iridescence or pale scaling to the wing-coverts, as shown above.

Adult Black-eared Cuckoo - showing contrasting pale grey rump against the dark wings and tail. This bird has fresh plumage and as such, because the feathers are not faded by UV light, this bird is a s dark as any BEC is likely to be. 

(2) The BEC has a contrasting pale rump and upper-tail coverts (this is only in adult BEC) as above. The HBC does not have a contrasting rump, nor does a first year BEC. A first year BEC has only a slightly paler rump, see second last image below.

Adult Black-eared Cuckoo - showing buff-cream underparts
and dark chevrons on the under-tail coverts

(3) The BEC has a uniform buff to cream underbody with dark chevrons on the under-tail coverts in an adult, as above, or with no markings in a 1st year birds, as below. The HBC has a mostly white underbody and unmarked under-tail coverts.

First-year Black-eared Cuckoo - showing no barring on under-tail coverts

(4) The patterns on the head are more bold in the BEC; the supercilium is broad and square-ended and the black eye-stripe ends in a broad patch on the ear-coverts, as in an adult shown below. The HBC has a narrower and duller supercilium and eye-stripe.

Adult Black-eared Cuckoo - showing facial markings

A first year BEC has no eye-stripe, but does have a dark patch around the ear-coverts. It also has a pale buff-cream supercilium, lores and throat, as below. The pale colouring of the lores is contiguous with the supercilium, whereas a HBC has dark lores in all plumages.

First-year Black-eared Cuckoo - showing facial markings

(5) The adult BEC has a uniformly dark brown upper tail, with no obvious iridescence (there is s slight glow in the illustration) and a contrasting white tip, as below. The HBC has no white tip, is iridescent and has rufous edges to the base.

Adult Black-eared cuckoo - top side of tail showing white tips

A first-year BEC has pale tips to a dull uniform coloured tail, as below.

1st year Black-eared Cuckoo - showing pale (not white) tips to tail
Also note pale grey rump, but not of high contrast with wing and tail colouring

(6) The underside of an adult BEC's tail also shows a white tip, as below, and lacks the obvious rufous markings on the HBC.

Adult Black-eared Cuckoo - showing underside of tail with white tips,
and dark chevrons on the under-tail coverts

In summary, the bird photographed by Kym has: (1) an obvious iridescence on the wing coverts, which also show distinct scaling on their edges (so it is not a BEC), (3) the underparts are off-white/grey, not buff/cream (so not a BEC) and the under-tail coverts are unmarked (so not an adult BEC), (4) the supercilium and eye-stripe are dull and narrow with tapering ends rather than square-ended near the ear (so not a BEC), and the lores are dark (so not a first year BEC). As rump and tail tips are out of view in Kym's photograph points (2) and (6) cannot be assessed. One further feature of note is the dark grey band across the bird 's throat in Kyms' photograph, this is not mentioned in the HANZAB description (I can't find such anyway) and it does not show in any of the BECs I have photographed, so this could be an additional distinguishing point.

Therefore, in conclusion, the bird photographed by Kym was a juvenile Horsefield's Bronze-Cuckoo.

For further points on Black-eared Cuckoo plumage and age refer to my previous blog posts of November and December 2013.

Black-eared Cuckoos

A first-year Black-eared Cuckoo on the left, adult on the right

In a recent post I discussed the plumage of a Black-eared Cuckoo Chrysococcyx osculans which we caught at Charcoal Tank Nature Reserve, then last weekend, 14-15 December, we caught the same bird again, along with two younger birds which were definitely in their first year. A useful comparison.

Once again I am grateful to Mark Clayton who organised the trip as part of a long-term study of birds in the area.

The second first-year bird

One of the first-year birds

The adult bird (right) as described in the earlier post, had a fully marked face and a richly coloured throat and breast.

 

Both first-year birds had faintly marked faces, with dull throat and breast colouring.














The moult sequence and timing of the various feathers of this species is poorly known, with the information used for the synopsis in the Handbook of Australian, New Zealand & Antarctic Birds being based in parts on only a sample of three birds. And we only have a sample of three. Therefore, I am open to discussion on any points raised.

The two young birds on the left have dull grey-brown rumps and tails; the adult bird on the right has a grey
rump contrasting with a dark tail. The first-year birds have faded feathering overall, while that of the
adult bird is fresh, unfaded and lustrous like other birds of the genus

Although synchronous growth bars on the tail are used as an indication of a bird with its original tail feathers, it seems from comparison between these birds that the adult bird might not really have synchronous bars. Perhaps the feathers can grow and align to seem to be of the same age. The freshness and dark unfaded colouring of the adult bird's tail would seem to be recently grown. Yet, apart from the apparent synchronous tail growth bars, the bird has an otherwise adult plumage. Also, its tail is only slightly worn at the tips, and it has distinct white tips, as mentioned in the previous note, unlike the first-year birds which both have well-worn buff tips. Such bold white tips (compared with buff tips of definite young birds) are often an indication of an adult bird. I suggest that this is indeed a true adult bird which hatched at least two breeding seasons ago, and the first-year birds hatched one breeding season ago.

The first-year birds also had faded, frayed secondary coverts with buff tips, and darker, unfrayed primary coverts

There is another trip to Charcoal tank planned for January, so perhaps if we catch these or any other Black-eared Cuckoos we will be able to note any moult  features which could help to determine this species moult pattern.