Date: 2/27/17 8:48 am
From: Gary Rosenberg <ghrosenberg...>
Subject: Re: [AZNMbirds] Sam Len Waterthrush Follow-up
Hi All,

I have received a number of emails pointing out that Louisiana Waterthrushes “have” occurred at still-water ponds in AZ in the past - and although I could not think of any when I made my comments, I stand corrected. My “point” was that, in Arizona in winter, one is MUCH more likely finding Louisiana Waterthrush along a stream or river - as THAT is its preferred habitat during winter. There are a few exceptions of likely migrants that have occurred at ponds (in AZ) - Willow Tank near Portal being one - but I will stand by my comments that a “wintering bird,” if this is indeed wintering here (at least present for more than a week), would more likely be a Northern based on habitat, and that should have been part of the thought process during the consideration as to what species we were dealing with. If one was interested in looking for Louisiana Waterthrushes in Arizona (or Mexico, or Costa Rica etc.) during the WINTER, I would concentrate on streams and rocky rivers, as opposed to ponds - etc…

During migration, particularly away from the West (where Louisiana is a very rare migrant at best), one can, of course, see Louisianas in a variety of habitats - not many rocky streams along the coast of Texas and Louisiana, where it is a regular migrant!

I do like the behavior differences mentioned by Phil - Louisianas “swish” their tails more side to side as compared to the up and down motion of Northerns - something else to look at when trying to ID one of those “tweener” waterthrushes.

Photos can be seen on Chris Benesh’s FB page at:

https://www.facebook.com/photo.php?fbid=10210936463383713&set=a.1064335964770.2011018.1117133130&type=3&theater <https://www.facebook.com/photo.php?fbid=10210936463383713&set=a.1064335964770.2011018.1117133130&type=3&theater>

Good Birding,

Gary



> :: they essentially occur along rivers and streams with running water
>
> As an East Coast birder who sees both waterthrushes each year, I'd like to chip in on this.
> We see Louisianas next to still water including muddy puddles a significant proportion of the time in Central Park (NYC) on migration and I've seen them in TX in the same context. I would not use this as an ID factor. Northerns are probably more prone to wander away from water - wet lawns and shaded cover, but that's also biased by Northerns being significantly more frequent through NYC.
>
> Amongst the other factors people have listed - which all seem reasonable to me - I haven't seen mention of one that may be useful - Northern bobs in a different way than Louisiana waggles. Northern bobs mostly it's tail with relatively little movement of the body beyond (head-side) the legs, closer to Palm or Prairie:
> https://www.youtube.com/watch?v=VcoF12ILFEw <https://www.youtube.com/watch?v=VcoF12ILFEw>
> - this bird also being useful as a pale NOWA for ID comparisons
>
> In contrast a Louisiana is much more articulated, and the legs bob as well, with the whole body rotating about an axis in the breast. Really only the head remains still.
> https://www.youtube.com/watch?v=Y4I7ZTzywIc <https://www.youtube.com/watch?v=Y4I7ZTzywIc>
> I didn't pick this one because the LOWA was feeding in still water, but it conveniently does go back to my original point.
>
> I use the motion as one of my ID criteria, behind supercilium and flank contrast, leg color (spring only), call note and streaking density/shape.

Cheers
Phil Jeffrey
Princeton NJ

Gary H. Rosenberg
Tucson, AZ
<ghrosenberg...>

http://www.avianjourneys.com
<info...>


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