Happy New Year to all who have been following our Island Ringing Project! We are back for the spring, which means, time to update our ageing systems. Remember that any 1st calendar year birds last autumn are now 2nd calendar birds (these are our young/juveniles), and any 2nd calendar year or older birds are now 3rd calendar year or older (our adults).

With that being said, let’s begin with our highlights from the month! We started off this month with not one, but TWO beautiful female White-tailed Robins! This makes a total of three White-tailed Robins caught in Fan Lau, and a total of 7 White-tailed Robins ever caught by the HKBWS team!

This individual showed a moult limit between the outermost 3 GCs, which have more of a dull-brown hue, loose quality and worn edges compared to the inner 7 post juvenile GCs. Thus this must be a 2nd calendar year female!

Next up was one of our third most commonly caught species at this site- a Common Emerald Dove! These guys are always skulking around our net sites, so it’s not super surprising we catch so many of them! Though ageing non-passerines is not easy, it seems that the juveniles of this species seem to retain some Primary Coverts which have a distinctive patterning to them.

That being said, the individual above did not appear to have any retained juvenile coverts. This either means that this is an adult (3rd calendar year or older), or a juvenile that has now fully moulted. Since we do not know the answer to this (yet!), we must age this bird as a 2nd calendar year or older!

During the latter part of the month, we ended up catching a Brown-flanked Bush Warbler! These are not super common catches for us, so it is always a privilege to see them up close! Bush Warblers are known for carrying out Summer Complete moults in both adults and juveniles, making them identical based on plumage. Therefore, we aged this bird as a 2nd calendar year or older.

Finally, we ended our chilly month with one of our most beautiful breeders: the Hainan Blue Flycatcher!

This male showed a supposedly uniform wing, with dark, dense and good quality feathers throughout. I say, ‘supposedly uniform’, as most flycatchers exhibit a winter partial moult (also known as a prebreeding moult) in both adults and juveniles. In theory, this means we should see moult limits in both adults and juveniles in spring. In reality, recognising the difference between adult post breeding feathers (from the Summer Complete moult) and prebreeding feathers (from the winter partial moult) is notoriously hard, as you are comparing adult type feathers that have just a few months age difference (note that once again, this is species specific). However, it is typically rather easy to tell juvenile feathers from prebreeding feathers. Therefore, despite not seeing these moult limits in the wing (possible some moulted tail feathers on the right side), we can conclude that this is a 3rd calendar year or older male!

A lovely month overall!

Daily Totals

*Please note that all wild birds, their nests, and eggs are highly protected (under Wild Animals Protection Ordinate, Cap. 170) in Hong Kong. It is an offence to wilfully disturb, take, remove, or injure wild birds or their nests/eggs. The actions described here were undertaken by trained professionals holding the necessary licenses and permits issued by the AFCD.*