Subject: Why more female Daurian redstarts? [Print This Page] Author: sgeoff Time: 1/02/2007 21:31 Subject: Why more female Daurian redstarts?
I have a query on the Mylamma flora and fauna forum that I cannot answer. Why are there many more female Daurian redstarts than males seen in Hong Kong? Is this the same in other locations?
I think because they are not all females. First winter birds, male and female, have the same dull colours as the adult female although there are probably some distinguishing features if you look closely enough. I don't have my books with me to comment on this bird.
The ratio of 'adult male' to 'other' on Po Toi is about 1 in 4. This is what you would expect if the 2 adults and 2 young from the year have survived to the winter. Is it the same ratio on Lamma? Author: sgeoff Time: 2/02/2007 20:36
Thanks Geoff. Maybe 1 in 4 on Lamma or even lower frequency I would guess. I had suspected that sub-adult males might resemble females, but I can't see anything about that in either Birds of China or Birds of Hong Kong. Does anyone have any detailed information on this? Author: wgeoff Time: 3/02/2007 14:46
Geoff
The best books I've found for first winter birds are the two Field Guides by Robson, one on the Birds of SE Asia and the other on the Birds of Thailand. I don't have them with me here in UK but I'm fairly sure they will have pictures of first winter Daurain Redstarts. Author: cgeoff Time: 3/02/2007 16:03
First-winter Daurian Redstarts look very similar to winter adult males.
I believe the reason for the difference is that the core wintering areas of males and females are different. This is the case for many species of passerine. Males often winter further north, possibly because they wish to be closer to the breeding grounds and so get a head start when returning to set up territories. Thus, it is likely that the further north you go in south China at this time of year, the greater the proportion of males.
Another species that seems to illustrate this is Red-flanked Bluetail. Proportionately more males occur further north in the winter, which is why when we have very cold spells in HK late in the winter, quite often we get an influx of males. I remember this was particularly evident during one late winter influx at Ng Tung Chai about 10 yrs ago. The males seem to be able to hold out further north for the whole winter, unless there is an unusually cold spell later on.
I've also noticed that more male Grey-backed Thrushes appear midwinter. Certainly, at the moment there seems to be a lot of males around, first-winter males especially.
Geoff Author: sgeoff Time: 3/02/2007 16:51
Interesting. That seems to answer the question.
Thanks Geoff
and thanks too Geoff
Geoff Author: wgeoff Time: 3/02/2007 20:27
Wrong again.
Thanks Geoff and Geoff, Geoff.
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