“It was an overcast and drizzly day and I decided to check up on some Glossy Swiftlets (Collocalia esculenta) that were nesting in an underground car park in the city.
“While I was there I walked up the car park to the fifth floor as I saw Pacific Swallows (Hirundo tahitica javanica) flying and wanted an opportunity to take pictures in flight at ‘eye level’. I used the ‘sports’ function on the Nikon D90 camera to enable fast tracking, kept the zoom at 200mm and was handheld for flexibility.
“I followed as many birds as possible, pulling in the zoom once I got focus, and trying my ‘luck’ for some pictures. Many were blurred but got some interesting pictures in flight.
“While watching them for about 20 minutes I noticed five episodes of altercations. Three of the episodes captured were unfocused picture but managed two episodes with some clarity.
“Posted here are the two episodes: above: a composite of two birds in conflict (the third bird was not involved here) and below: two single pictures in sequence of another conflict (the third bird involved here).
“I was puzzled by the behavior. You can see that there was actual physical contact, although much of it was aerial pursuits and calls (‘shouting’). There were 6-7 Pacific Swallows at the site and I considered a number of possibilities for the behavior:
1. Firstly I considered mating conflicts as often it was two birds in conflict with a third watching.
2. Second possibility was territorial disputes but this is a high rise building, lots of space and did not seem likely.
3. Only after processing the images did the third possibility emerged – I think what is happening here is that juveniles (now immature adults) are still begging parents for food but parents have reached that stage where its time for the immature adults to forage on their own. I have seen this type of behavior often, especially with continual/daily observation in our garden, of a number of species. The immature/overgrown juveniles continue to harass parents for food even though they should be able to forage themselves. They chase parents from perch to perch, until finally parents reach a point and “retaliate”.
“If you look carefully at the composite (focus on bottom right frame first) you will notice that the bird in front has bold white ‘windows’ on the tail feathers at T2-6 (see Wells, 2007) that indicate it is an adult. But in the bird behind, these are hard to see and only appear as ‘pale dots’ indicating the bird is a juvenile (immature adult). Also notice the immature look at the mouth.
“In the second series (focus on Pacific Swallow-fight-3a) notice the adult on the left who was ‘supporting’, the juvenile in the middle and another adult on the right (shying away).
“Now the problem I am facing. Appreciate some opinion of my earlier post & this one.
“Notice these two pictures I have labeled one as adult in flight (below left)) and the other as immature in flight (below right). But even the one with bold white ‘windows’ on the tail feathers looks immature at the mouth. To compound the issue, I post a juvenile (Pacific Swallow-Juvenile on wire-6a), from an earlier trip, that has clear bold white ‘windows’ on the tail feathers (below).”
Dato’ Dr Amar-Singh HSS
Ipoh City, Perak, Malaysia
30th June 2010
Krys Kazmierczak responded to Amar’s problems: “I’m not sure about the difference in whiteness of the spots between adults and juveniles, but the visibility of the spots of course depends on how much the tail is spread. Since the spots are on the inner webs of the tail feathers T2 to T6, they are mostly covered by the (spotless) outer webs of the tail feathers which overlap them when viewed from above. Thus they only really stand out when the tail is completely spread. The spots are totally invisible, although present, when the tail is only partly spread and viewed from above (above right). If the tail is spread more than that, but not as much (above left), then the spots will simply appear smaller and duller, because they are partly covered by the outer webs of the tail feathers above them. I don’t know if that helps.”