Wednesday, 21 February 2018

Fan-tailed and Brush Cuckoos

Over many years of birding I have never seen a Fan-tailed Cuckoo (Cacomantis flabelliformis) fan its tail and if you have never seen one do this either, then you are not alone. Only one of the five popular Australian birding guides mentions tail fanning and suggests the bird infrequently fans its tail. From my experience tail fanning in this species is less than infrequent!

So how did this cuckoo get such an inappropriate name? In Australian Bird Names, A Complete Guide. Ian Fraser and Jeannie Gray point out the name was given by John Latham who never saw a live Fan-tailed Cuckoo.

Why Latham thought they fanned their tails will probably remain a mystery.

Please click on photos to enlarge.

Adult Fan-tailed Cuckoo – back and top-of-tail view.

Another adult Fan-tailed Cuckoo showing the light rufous front and under parts.

I suspect the above bird is a male given the more extensive light rufous colour of the front parts and the bird below is a female as the rufous colour is restricted to the throat area.

Female adult Fan-tailed Cuckoo.

Fan-tailed Cuckoos are brood parasites laying their eggs in host or foster parent nests. The field guides indicate birds that build domed nests are selected by Fan-tailed Cuckoos and a couple of guides mention that the cup shaped nests of some honeyeaters and flycatchers are infrequently used.

Recently I found a juvenile Cuckoo perched and begging for food, so I set my camera up and focused on the young bird and waited to capture the host parent come in with food, while wondering what species it would be.

Juvenile Cuckoo waiting to be fed and begging with calls and wing fluttering.

Even though I knew the host parent would come in and I was ready to capture the event, I was too slow and only managed to capture one photo of the host parent shortly after it delivered the food item. I was surprised to discover the host was a Rufous Fantail, a cup nest builder.

The Rufous Fantail has just fed the juvenile Cuckoo.

Typical of the energetic and rarely-stands-still Rufous Fantail the foster parent was gone in a flash.

The juvenile looks to where its foster parent headed. A second later the juvenile followed.

I must admit that I assumed without checking that the above juvenile was a Fan-tailed Cuckoo which are the most common cuckoo species in the area where I photographed the young bird. Following a query of my assumed ID I checked the field guides and found the juvenile was the much less common Brush Cuckoo. The juvenile Brush have a more boldly patterned back and upper wings compared with the Fan-tailed juvenile.

An adult Brush Cuckoo which is superficially like the Fan-tailed Cuckoo but perhaps most notably lacks a yellow eye ring.

A further check of the field guides showed the Brush Cuckoo parasitises bird species which build cup nests and not domed nests – in retrospect this was another clue that my assumption of a Fan-tailed Cuckoo juvenile was wrong, given Fan-tails rarely use cup nests.

A few days earlier in another location I captured a photo of a Fan-tailed Cuckoo juvenile which had moulted to a stage in between a juvenile bird and a full adult. Apparently the first fledged juvenile plumage is soon replaced by adult plumage. The juvenile in the photo below has a bright yellow eye ring and the slate grey head and back feathers are emerging.

A more advanced juvenile with yellow eye ring and new adult feathers emerging.

Observing and absorbing all the details of birds in the field can be a challenge. But capturing and then examining photos on a computer screen back at home with field guides and a cup tea or something stronger at hand is a great way to pick up more details and learn more about these intriguing avian creatures. That said if you have a preconceived idea of what a species is then you may fail, as I did in this case, to check the field guides and then miss reaching the right ID for a bird – this can be particularly tricky when dealing with juvenile birds.

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