Thursday, 20 July 2017

I Lost My Jaeger MOJO

On Saturday 15 July 2017 I ran into some jaeger feeding action at St. Vincents Beach on the southern Avalon Peninsula. The capelin and humpback whales were in. Kittiwakes and terns were hunting for capelin near the surf.  I soon realized there were jaegers as well.  Subadult jaegers are typically part of the capelin feeding smorgasbord usually hanging a few hundred meters offshore harassing the birds but today the jaegers were coming in over the beach after kittiwakes and terns carrying fish. Often these jaegers go unidentified because they lack central tails feathers and views are not close enough for plumage details. The 2nd years may have a semblance of adult tail. We identify that bird to species and then compare the size and actions to others that bird to help with our IDs.  Generally most are Pomarines. It usually takes a while to nail down a Parasitic Jaeger. Very uncommonly is there a subadult Long-tailed Jaeger among these capelin birds. Yet subadult Long tails are routine in the offshore zones 200-400 km offshore eastern and southern Newfoundland.  It is practically the default jaeger mid June to early August.

I quickly identified some of the 15 July jaegers as Parasitics by the tiny pointed central tail feather projections eliminating Pomarine. Even on the birds I could not see this feature, the manner in which they chased kittiwakes with capelin was in the Parasitic style = strong powerful flights low over the water to a target followed by a fierce aerial chase full of rapid twists and turns for extended periods of time.  Poms do this but usually call off the chase sooner.  Long-tailed Jaegers, in Newfoundland waters at least, only occasionally chase birds and then somewhat half halfheartedly.  They spend more time playfully chasing one another than other birds. (An exception to this was off NE Greenland where I saw adult LTJAs regularly and purposefully chasing kittiwakes, Ivory Gulls and Arctic Terns.)

Long-tailed Jaeger hardly even entered the equation at St. Vincents Beach. None of the birds were acting like Long-tailed Jaegers.  Everything was either a Parasitic or a Pomarine and then identified as Parasitic by central tail feather. In total I think there were 10 Parasitic Jaegers. Saw up to 8 at one time.  And no Pomarine. The photography opportunities were exceptional so that is what I targeted for the next three hours. The jaegers were mostly resting 300 m offshore between raids on the feeding kittiwakes and terns feeding among the surf.

It seems I photographed only three different individuals. One was a darkish bird. Seemed fine for a Parasitic but I was rather shocked by the photos of the other two.  Features I would look for on 1st summer Long-tailed Jaegers were obvious on these bird.  Features like white primary shafts restricted to outer two primaries, narrow rear and tail, highly checkered dark and white tail coverts and blond heads, frail thin body, possibly small head and bills.  This surprised me. I admit to never looking at the birds with binoculars when close but always through the camera.  The birds were acting so much like Parasitic Jaegers I didn't think Long-tailed Jaeger was a possibility.

I have more research to do yet but after a couples days of thinking about the scene I am hedging toward all the birds being Parasitic with no Long-tailed.  Parasitic Jaeger of all ages is the jaeger I am least familiar with. Lots to learn.

Below are photos of the three birds.  

BIRD # 1





Note how number of pale primary shafts changes with the angle of light but the two outer most were the brightest and often the only two showing up as white in the photographs.






BIRD # 2

Bird # 1 on Left, Bird # 2 on Right

Bird # 2 Left, Bird # 1 on Right

Is there a jaeger watcher out there does not automatically think Long-tailed Jaeger when they see this!?





A different angle to the sun makes more than the two outer primaries look pale.




BIRD # 3






I am sticking with my original identification in the field that these three birds are 1st summer Parasitic Jaegers.  I admit to being surprised by the two pale birds and how closely they fit into my mental image library of Long-tailed Jaeger.  The library shelf for Parasitic Jaeger images is unfortunately sparse. Would be happy to hear opinions from others on these birds.  You may leave a comment at the end of this Blog or email me at brucemactavish1 AT gmail.com  The bill on the photo above looks long and narrow for a LTJA - doesn't it!?



4 comments:



  1. Brandon Holden
    to me
    0 minutes agoDetails

    I am inclined to say every photo is of LTJA! Thin wings, thin body, widest at the breast, two white shafts, small underwing flash, thick/short bill (although I agree the last photo is showing trickery) - and maybe even the bicoloured secontaries vs. coverts?...

    Obvious caveat is that some of these features are shared between the species, and also that I've been wrong before (that one time I thought I was wrong, but wasn't)... But I'm going with LTJA without regret!

    Nodnarb Nedloh

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    Replies
    1. sorry this posted so terribly... apparently work doesn't want me commenting on Jaegers... Having some second thoughts on bird #3, but I'll wait and see what others think (photos show a body shape that jives less with LTJA in my mind, and it's harder to see all the features).

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  2. ahh the joy of juvenile jaegers. great post I know a couple of jaeger experts who could answer these with 100% accuracy send me an email Bruce if you want their emails.

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  3. I am inclined to think that these are all LTJA, for reasons outlined by Brandon. Plumage-wise, all three strike me by having no prominent white flash on the underside of the primaries, which should be glaring in Parasitic. #1 has a bit of one, but its split. Its as though LTJAs have a P10 borrowed from a big curlew. #2 looks quite classic, as you mentioned, and seems to be sized and structured the same as #1 in their together portraits. #1 seems objectively smaller than that kittiwake in every respect. Wing chord alone is clearly shorter, yet the smallest female Parasitics should still have a longer wing chord than the largest male Kittiwakes. #3s plumage and structure seems fine to be. That bill looks short to me... half black and half grey, chin feathering going way up to near that puny gonys.

    Here's some fresh meat to look at: http://ebird.org/ebird/view/checklist?subID=S38405998
    (I think IDs are ok except PAJA#1 which I think is a Long-tailed)

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