I observed two nesting episodes of the Copper-throated Sunbird Leptocoma calcostetha at the Matang Mangrove Forest Reserve, Perak, and would like to share my observations.
On 1 June 2023 I observed an adult female Copper-throated Sunbird building the early stages of a nest. The nest is anchored to a thin outer branch of a tall mangrove tree (see Image 1). What was unusual was the height of the nest. Wells (2007) describes nests as suspended at heights of 0·7–3·5 meters above ground from a thin mangrove branch or frond tip. Cheke and Mann (2001) describe nests as anchored “from less than 1 to about 2.5 meters above ground”. The nest I saw in construction was anchored 9-10 meters up.
I only saw the female involved in nest building activities (see Image 2).
New material was added every 3-5 minutes. The nest was constructed of dead plant material – strips of vegetation, dead leaves and twigs (see Image 3). Spider web was used to hold sections together. A considerable amount of ‘cotton’ from the Kapok tree (Ceiba pentandra) had been added to the nest.
I saw the adult male visit once but it was not for nest building but courtship. Both birds flew off together, singing loudly, and displaying. I have previously described their courtship behaviour (Amar-Singh HSS 2022).
The second nest I observed at the Matang Mangrove Forest Reserve was on 24 February 2022. Some colleagues kindly alerted me to the presence of the nesting birds.
The second nest was more ‘conventional’ in height location; it was located about one meter above the ground. The nest was anchored to the stem of an Acrostichum fern and had a ‘tail’ (see Image 4).
The juveniles were being fed. The female would often, after feeding, enter the nest to keep the young warm; suggesting juveniles were still very young. From 7.50am to 10.00am, I observed at least 10 feeding episodes; 8 by female and 2 by male. On 2 occasions I saw faecal sacs removal by the female (see Image 5). I was uncertain if the faecal sacs were eaten by the adult.
The feeding items brought to the juvenile Copper-throated Sunbirds were difficult to ascertain, as the nest opening was turned away from observers. However, the adults spent much time checking tree foliage and bushes for small animal prey, presumably insects. I did not see any spiders taken but I did see spider webs on the bird’s beaks. I suspect that the birds collect nectar to feed the chicks. I observed the adult female move often from visiting the mangrove flowers directly to the nest. Bruguiera sexangula (commonly called the Upriver Orange Mangrove, or locally Tumu Putih) is used as a nectar source (see Image 6).
There were quite a number of other Copper-throated Sunbirds around at the same time and I was privileged to watch a courtship ritual and mating.
References:
1. Wells, D.R. (2007). The Birds of the Thai-Malay Peninsula: Vol. 2 (Passerines). Christopher Helm, London.
2. Robert A Cheke, Clive F Mann, Richard Allen (2001). Sunbirds: A Guide to the Sunbirds, Flowerpeckers, Spiderhunters and Sugarbirds of the World. Helm Identification Guides
3. Amar-Singh HSS (2022). Courtship Behaviour of the Copper-throated Sunbirds. Bird Ecology Study Group. https://besgroup.org/2022/02/26/courtship-behaviour-of-the-copper-throated-sunbirds/