Further to my request yesterday and comments from James Bradley it does appear that extreme care is needed when encountering melanistic coastal cuckoos, and that the movements of these birds remains largely unclear.
The first example of such a cuckoo was back in 1879 when one was collected by Sir John Kirk’s collectors in the Pangani River Valley below the East Usambara Mts, and which is currently housed in the Natural History Museum at Tring, UK. In 1881 it was named Coccystes albonotatus and was considered at the time a dark morph of the South African C serratus. It was not until later that Grant & Mackworth-Praed (1936) looked at a small series of similar melanistic individuals from the East Africa coast did they determine that all were in fact melanistic C cafer (the earlier name attributed to C levaillantii).
Separation in the field of melanistic C jacobinus serratus from this melanistic form of C levaillantii is extremely difficult and possibly impossible unless handled. The slightly larger C levaillantii may also be subject to as yet undetermined movements as most records seem to fall into the coastal rainy seasons, while the migratory bird from Southern Africa can only be expected during the May-September period.
James himself observed a melanistic cuckoo at Msambweni in February 2014, which fitted well with the slightly larger Levaillant’s.
Meanwhile the two photos posted this morning from Doris at Lake Jilore in July this year are exactly as I recall my coastal birds years ago.
When I lived at Mombasa in the late 50’s these all-black cuckoos were certainly present in the Bamburu area to the north of the town during the May-July rains, but I had no records of them outside of that wet season, nor was I confident at the time to assign them to any particular species. Books available at the time did not really help; Praed & Grant made no mention of any coastal melanistic cuckoos, and it was only Jackson who considered these melanistic birds to be the Southern African migratory serratus.
Levaillant’s Cuckoo parasitizes Arrow-marked Babblers almost exclusively, yet none occur in the Kenya coastal lowlands, but they do occur on the Tanzania coast from Dar-es-Salaam north to the Pangani River, itself suggestive that they may not be resident on the Kenya coast, instead occurring only during the seasonal rains there.
May I ask that everyone takes full details of any melanistic cuckoo encountered at the coast. Photographs and dates would be invaluable.
At the moment all we can say with any degree of certainty is that:
I). There are melanistic forms of both Jacobin and Levaillant’s cuckoos, with the latter being the larger, longer winged and longer-tailed of the two.
ii). All-dark Levaillant’s appear to be known only from the East African coast from Malindi south to the Tanga and Pangani regions of northeast Tanzania, and there are several specimens to support this.
iii).The slightly smaller all-dark Jacobin Cuckoos (serratus) can be expected in the East African coastal lowlands during the May-September period.
iv). I wonder what Neil Baker can add to all this from his Tanzania Atlas records ??
Best wishes
Don Turner