Date: 4/24/24 7:01 pm From: Johnson, Erik via groups.io <Erik.Johnson...> Subject: Re: [labird] SEG Environmental Chandeleur Islands Trip 23 April 2024
LAbird,
I looked up cuckoo continental population estimates in the Partners in Flight Database, which is largely based on USGS Breeding Bird Survey data. About 8.4 million Yellow-billed Cuckoos in the U.S. and Canada versus about 0.9 million Black-billed Cuckoos, or a 10:1 ratio.
(https://pif.birdconservancy.org/population-estimate-database-scores/)
So why the 100:1 ratio detected in migration per Van (I'm inclined to agree with that). Interesting that with a low sample, Robb got more of a 10:1 ratio in nocturnal flight - would be interesting to know how that stacks up across a season, or multiple seasons.
My hunch is that Black-billed Cuckoo is more of a long-distance jumper than Yellow-billed Cuckoo, which may be better described as a short-distance skipper. The corollary is that Black-billed would pass through faster, thus is less available for detection.
An alternative (or contributing factor) is that Black-bills are a lot less easy to detect, but I just don't believe that Yellow-billed Cuckoo is 10x as likely to be detected as a Black-billed. Black-bills do seem to be a lot less vocal, however, so maybe that's some of it.
Someone needs to do a migration tracking study on Black-billed Cuckoos! Only 3 Motus tags ever deployed, and no other tracking information seems to be published.
Happy migration!
Erik Johnson
Sunset, LA
Erik.Johnson AT Audubon.org
-----Original Message-----
From: <labird...> <labird...> On Behalf Of Robb Brumfield via groups.io
Sent: Wednesday, April 24, 2024 8:22 PM
To: James V Remsen <najames...>; Jack Rogers <jack...>
Cc: LABIRD <labird...>
Subject: Re: [labird] SEG Environmental Chandeleur Islands Trip 23 April 2024
From my nocturnal flight call station in Baton Rouge the evening of April 22nd was a season high for migrating cuckoos. Between 9:30 pm and 3:30 am (April 23rd) I had 24 individual yellow-billed and 2 black-billed.
Robb
Robb T. Brumfield, PhD
Associate Dean of Research & Administration, College of Science Roy Paul Daniels Professor of Biological Sciences Curator of Genetic Resources, Museum of Natural Science Louisiana State University | lsu.edu |science.lsu.edu/
office: 225-578-4206|mobile: 225-202-8892|fax: 225-578-8826 <robb...><mailto:<robb...>
From: <labird...> <labird...> on behalf of James V Remsen via groups.io <najames...>
Date: Wednesday, April 24, 2024 at 7:49 PM
To: Jack Rogers <jack...>
Cc: LABIRD <labird...>
Subject: Re: [labird] SEG Environmental Chandeleur Islands Trip 23 April 2024 Jack et al. — wow, what an experience! Fascinating.
As for the cuckoo prevalence …. Another hypothesis is that it was just one of those “cuckoo waves”. Spring waves are often dominated by one taxonomic category. For example, sometimes there are “cardinaline days" with buntings, grosbeaks, and Dickcissels making up the bulk of the migrants. Rarely there are “thrush days, with Catharus species and Wood Thrush predominating. Sometimes warblers steal the show. Sometimes Catbirds or R-e Vireos are way over-represented.
As fo YB vs. BB cuckoos — indeed it’s pretty clear that YB is a common bird with a huge overall population, and BB is generally scarce. Although YB has a larger breeding distribution, the difference is small compared to the ratio of migrants detected, which I suspect is at least 100:1. Why the disparity is so great is a mystery to me and to my buddies with whom I’ve discussed this on long birding trips. My personal high count for BB is 5, way back in April 1979, and nowadays, seeing more than 1 in day is a big deal. There have been years when I’ve not seen one at all.
Van Remsen
===================
Dr. J. V. Remsen
Emeritus Prof. of Natural Science and Curator of Birds Museum of Natural Science/Dept. Biological Sciences LSU, Baton Rouge, LA 70803 najames<at>LSU.edu
> On Apr 24, 2024, at 5:01 PM, Jack Rogers via groups.io <jack...> wrote:
>
> [You don't often get email from <jack...> Learn why
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>
> LaBird
> I hope you all have been having a birdy spring! Hopefully we get one
> more front before the end of the month--these south winds have been killing me!
> I wanted to write to talk about the crazy day on the Chandeleurs that
> we had yesterday. As part of an ongoing survey by SEG Environmental,
> we bird the island once a month looking to assess the numbers of
> several target species (Red Knot, Chandeleur Gull, Wilson's/Piping/Snowy Plovers, etc.).
> I think that we have all been most excited for the April survey, and
> it definitely lived up to expectations.
>
> For those that have not had the pleasure of visiting the Chandeleurs,
> it is an amazing place. Most (I would estimate over 90%) of the
> island's vegetation is Saltmarsh Cordgrass (Spartina alterniflora); in
> some of the slightly higher elevation areas, there is also Phragmites
> and Groundsel as well. Matt Conn and I surveyed the northern tip of
> Chandeleur Island, which has almost no vegetation except for Spartina.
> The birding was nothing short of excellent-we had 81 species (+1
> Chandeleur Gull), which I think is pretty great considering there is
> only 1 tree in that section (a 6 ft tall Mangrove). There were about
> 7 small mounds in the saltmarsh that had small groundsel bushes or
> Phragmites stands. Each bush or stand of Phragmites was astoundingly
> full of migrants. Take a look at our eBird checklist here
> <https://ebird.org/checklist/S170012706<https://ebird.org/checklist/S1 > 70012706>> for the full rundown. My personal highlight was the best
> Black-billed Cuckoo looks I can ask for! I know several other groups
> had great birds as well: Cape May Warbler (x2), Yellow Rail (!!), and Blackpoll Warblers were seen by other surveyors on their more southerly transects.
>
> I was most interested by the incredible density of Cuckoos compared to
> smaller migrants (e.g. warblers, buntings, etc). The only thing I can
> think of is that there is really nothing for cuckoos to eat on the islands:
> there is no fruit, no insects much larger than saltmarsh moths or
> horseflies, nothing that Cuckoos could theoretically refuel themselves
> with after a trans-Gulf flight. Whereas there are plenty of tiny
> insects (aphids, mosquitos, miniscule beetles and saltmarsh flies) for
> warblers to eat, and plenty of seeds for INBUs etc. I also found the
> ratio of Yellow- to Black-billed Cuckoos interesting. I believe that
> Matt and I had a 100% detection rate of Cuckoos within our section,
> and am pretty positive in a 100% correct identification rate as well.
> I have always thought that my lack of mainland BB Cuckoos was a
> detection error, but now I am wondering if it is more of a disparity in population sizes.
>
> I wrote this in my eBird comments, but this was really one of the most
> exciting days of birding in my life. Small groundsel bushes (2 feet
> high with a diameter of 18 inches) were holding ridiculous totals of
> birds such as one that held 7 Y-b Cuckoos, 3 Catbirds, 2 Ovenbirds, 1
> Swainson's Thrush, and 2 Yellow Warblers. An absolutely incredible
> experience, and just wanted to share that with you all.
> Thanks for reading this monologue and good birding to y'all, Jack
> Rogers
>
> --
> Jack Rogers
> LSU Renewable Natural Resources
> Baton Rouge, Louisiana/Mt Pleasant, SC My Flickr page
> <http://www.flickr.com/photos/90726323@N05/<http://www.flickr.com/phot > os/90726323@N05/>>
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