Choo Teik Ju a.k.a. choo located an adult, non-breeding Tiger Shrike (Lanius tigrinus) in Singapore in December 2008 (left).
Earlier, KC Tsang queried why only juvenile Tiger Shrike were seen in Singapore. This post got R Subaraj responding, saying that this is not so…
“It is not true that adult Tiger Shrikes do not reach Singapore! We do observe a few adults each winter. However, there are far more juveniles than adu,ts.
“Many adults tend to either arrive early in the season or fly stright through. We also encounter adults in spring, when they are on their way back. It is also possible that adults take up winter territories further north while juveniles are forced to migrate further….but this needs to be proven.
“There definitely seem to be more adult Brown Shrikes than Tigers each year.
“There are also far more immature or female Yellow-rumped and Mugimaki Flycatchers and Siberian Blue Robins each year than adult males! Many male Blue Robins do migrate through early.”
When sent the image by Teik Ju, KC responded, ”No not fully adult yet … still having that brown tinge on it’s forehead of a juvenile …”
According to Gll (2007), many species of birds undertake what is known as differential migration. What this means is that sexes and age classes of fully migratory species move different distances. Typically, females migrate farther than males and juveniles migrate further than adults. It is possible that males need to return to their breeding grounds early to claim their territories. But why juveniles fly furthest?
Image by Choo Teik Ju.
Gill, F. B., 2007. Ornithology. W. H. Freeman & Co., New York. 758 pp
This post is a cooperative effort between www.naturepixels.org and BESG to bring the study of bird behaviour through photography to a wider audience.
Yes I have also photographed an adult Tiger Shrike at Fort Canning Park, Singapore sometime back.
Lee Chiu San
Subaraj has a very good point that the adults might not migrate as far as the juveniles.
Among non-migratory birds with strong territorial instincts, the adult males boot the youngsters out to not very desirable territories on the fringes.
It could be possible that the shrikes need not need to come all the way to Singapore to find good wintering grounds. The adult males could reserve these (with packets of tissue?) and tell the youngsters to move off.
I can well imagine that a territory further north would be preferred, since it would be closer to the summer breeding grounds.
Tou Jing Yi: Why juveniles fly further away? haha….. maybe they do not know which exit to take, parents didnt tell them clearly, but juveniles seemed to be the common ones to overshoot anyway, same to Amur Falcon, while adults find no problem to turn towards India, some juveniles overshoot down south to Malaysia….. probably with experience, they understand they dont have to fly that far south for winter or merely know where they should be heading better? just some wild theories…