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Insight into the mixed-species bulbul breeding

on 23rd August 2009

The two earlier posts on a Sooty-headed Bulbul (Pycnonotus aurigaster) and a Yellow-vented Bulbul (P. goiavier) pairing up and starting a family (see here: 1 and 2) got a further attention from our bird behaviourist, John Vickerman, who wrote from his base in the United Kingdom:

“Thanks for keeping me updated with the developments of this mixed pair of bulbuls.

“Although there must be uncertainty still, I suspect, based on the behaviour shown in the pictures, that the adult male of the pair is the Yellow-vented for the following reasons:-

1. It is the Yellow-vented that appears to be taking the initiative in the mutual preening. Both sexes of many bird species do preen each other but it is generally the male that instigates the process. There is only one picture here to go on with this behaviour so it can only be a speculative guess.

2. However, this guess is strengthened when we see the two birds perched side by side on the irrigation tap. It is the Yellow-vented that is, though only very slightly because it is the highest point available, the higher of the two birds. Males tend to occupy the higher perches demonstrating strength and dominance to a prospective or established mate.

3. The bird carrying the fruit food for the juvenile is the Sooty. Although both sexes of most birds feed their young, the females tend to show a greater maternal instinct and feed young birds more often, so I would suggest the Sooty is the female bird.

“My guess is that this pair of adults has been significantly less successful in producing young than would a same-species pair in that I would expect a same-species pairing to raise more than just one juvenile to the fledging stage. If true, then this would consolidate well proven data that hybrid pairings, generally, are less productive than same-species pairings thus reducing the proliferation of hybrid birds in the wild”.

“The sex of the juvenile hybrid will remain unknown for quite a while. Whether it is fertile or not – whether male or female or sexless – remains to be seen given that it survives to potential breeding age. However, its ability to survive as “the odd one out” in the wild and even to attract and be selected as a mate at some stage – even if it is fertile – mean its chances of continuing the hybrid line are much lessened.

“It would be very interesting for recording purposes if Lee Tiah Khee or GS Soh, or anybody else, are able to continue monitoring the activities of this hybrid juvenile to watch its behaviour in the future, and to continue monitoring also any further breeding attempts that the adult pair may make in the future.”

If you like this post please tap on the Like button at the left bottom of page. Any views and opinions expressed in this article are solely those of the authors/contributors, and are not endorsed by the Lee Kong Chian Natural History Museum (LKCNHM, NUS) or its affiliated institutions. Readers are encouraged to use their discretion before making any decisions or judgements based on the information presented.

YC Wee

Dr Wee played a significant role as a green advocate in Singapore through his extensive involvement in various organizations and committees: as Secretary and Chairman for the Malayan Nature Society (Singapore Branch), and with the Nature Society (Singapore) as founding President (1978-1995). He has also served in the Nature Reserve Board (1987-1989), Nature Reserves Committee (1990-1996), National Council on the Environment/Singapore Environment Council (1992-1996), Work-Group on Nature Conservation (1992) and Inter-Varsity Council on the Environment (1995-1997). He is Patron of the Singapore Gardening Society and was appointed Honorary Museum Associate of the Lee Kong Chian Natural History Museum (LKCNHM) in 2012. In 2005, Dr Wee started the Bird Ecology Study Group. With more than 6,000 entries, the website has become a valuable resource consulted by students, birdwatchers and researchers locally and internationally. The views and opinions expressed in this article are his own, and do not represent those of LKCNHM, the National University of Singapore or its affiliated institutions.

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