Very interesting, Bob. Thank you for writing down all this information.
I am wondering if anyone has tried to do a population survey
accounstically. If these birds are consistent singers, it might be the case
that one can perform a population survey by analysis of sound recorded at
the nesting sites. Nowadays, there are sophisticated signal processing
algorithms that can separate a great many sources.
Regards to all, Steve
On Sun, Jun 16, 2024 at 8:44 PM Bob Boekelheide via Tweeters <
tweeters at u.washington.edu> wrote:
>
Hi, Tim and Tweeters,
>
>
I spent a few years studying Cassin's Auklets at the Farallon Islands, so
>
I'll try to answer your auklet questions.
>
>
If conditions are favorable, Cassin's Auklets at the Farallones mostly
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feed krill to their chicks. In less favorable years, they switch to eating
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a more diverse diet of larval fish and other pelagic crustaceans, along
>
with occasional small squid. They feed mostly in loose groups at the edges
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of the continental shelf, so they might fly considerable distances from
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their coastal nesting colonies to feed during the day. Sometimes you see
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big feeding groups of them, likely if there is a patch of krill, but
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they're usually more spread out.
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They fly back and forth to and from their colony every day, ideally not
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too far, but regularly 20-40 miles to feeding areas, often more. A
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Cassin's Auklet might travel 40-45 mph in fast flight depending on winds,
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so 20-40 miles doesn't seem too far for them. In poor feeding years they
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might have to travel much further to find food, or return smaller meal
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loads to their chicks, or else give up.
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>
They are totally nocturnal on land, other than of course during the
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nesting season when one adult stays in their burrow all day incubating
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their egg or brooding their young chick. They leave their chick alone in
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the burrow at a fairly young age, so both parents can return food to the
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chick. Their flights ashore to nesting islands occur well after dark, as
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they are sensitive to light levels even at night. Because of predation,
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they are slow to come onshore during moon-lit nights, but on dark moonless
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nights they come ashore right away. Sometimes they all come ashore in a
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giant wave, and sometimes they trickle in over a long period. They seem to
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be able to locate things fairly well even on dark nights, so they must have
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excellent night vision. Most departures in the morning occur well before
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dawn, but there are sometimes late departures that may end up in the belly
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of a gull or a Peregrine Falcon.
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>
When flying ashore, they usually fly in very quickly, plop down, get their
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bearings, and quickly make their way to their burrows. They often collide
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with things on their way, including people, but almost always they quickly
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shake it off and keep going. They do everything they can to avoid predation
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by gulls, which nest nearby and lurk in the auklet colonies at night. The
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auklets dig their own burrows or else nest in rock piles or rock cavities.
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Most burrows are about 2 to 4 ft deep, so once inside predators hopefully
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can't get to them. Breeding pairs are very faithful to their burrows
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between years.
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Cassin's Auklet adults have a nifty sublingual (under-tongue) pouch they
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use to carry prey to their chicks. The consistency of the goo they carry
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in their sub-lingual pouch is kind of like shrimp cocktail, which they lap
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out to the chicks when they reach the burrows. Meal loads with krill are
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mostly pink because of their photophores, whereas meal loads with fish are
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mostly gray fish chyme. We randomly captured auklets flying in with
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pouches full of food and sampled their pouch contents. It's quite amazing
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how large their meal loads can be relative to the size of the bird -; a
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180-200 g adult sometimes carried a 40-50 g meal load, or about 1/4 of
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their body weight. They can cram a lot of krill and larval fish into their
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bulging sub-lingual pouch.
>
>
Unfortunately many Cassin's Auklet populations have been shrinking,
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between marine heat waves, El Ninos, predation, and who knows what. The
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50,000 auklets estimated nesting on Alexander Island by Speich and Wahl in
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the 1970s might be much smaller now. But realistically, how do you
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estimate the numbers of a small seabird that only comes ashore at night on
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remote islands and then nests out-of-sight in underground burrows? It's a
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shot in the dark -; ha ha!
>
>
The best thing about Cassin's Auklets is their singing -; imagine thousands
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of them chirping away on a windswept island in the middle of the night.
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They scream their three-note songs while sitting in their burrows,
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repeating things like "LET ME OUT, LET ME OUT, LET ME OUT" and "IT'S ALL
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RIGHT, IT'S ALL RIGHT, IT'S ALL RIGHT," over and over. Totally wild!
>
>
Hope this helps,
>
Bob Boekelheide
>
Sequim
>
>
*From: *Tim Brennan via Tweeters <tweeters at u.washington.edu>
>
*Subject: **[Tweeters] How do Cassin's Auklets work?*
>
*Date: *June 14, 2024 at 7:33:14 PM PDT
>
*To: *"tweeters at u.washington.edu" <tweeters at u.washington.edu>
>
*Reply-To: *Tim Brennan <tsbrennan at hotmail.com>
>
>
Hey Tweets!
>
>
I've been plugging away at the Jefferson and Kitsap County year lists, and
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most recently made a trip to the coast, adding 8 more birds to the year
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list. This included some Black Swifts over a meadow behind a gift shop on
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the way up to the Hoh, and a few stray pelicans. 169 for the year in
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Jefferson was a Common Nighthawk over a clear cut (clearcut? Clear-cut?)
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off of FR-3000 the other night.
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The goal is two hundred species for the year. My bet is that I'll come up
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a little short of that, but have a great time trying. One thing that has
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been eluding me is some open-minded conversations about seabirds, and maybe
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more specifically, I am trying to understand Cassin's Auklets. A couple
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things I do understand about them. They are usually seen very far out from
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shore. Yep. The pelagic trips from westport head out far enough, but not
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into Jefferson. Repositioning cruises pass through Jefferson waters, but
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they pass through a lot of other waters, to my understanding, and might be
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a more extended trip than I'd be keen on doing.
>
>
So, I've researched a little, and come across an interesting fact. 50,000
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or so Cassin's Auklets nest on Alexander Island, Jefferson County. And this
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is like... A mile off shore. They go out far. I understand this. 😄 But...
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Then they come back, yes? Is their return usually in full dark? Late in the
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day? It may be information that's hard to pull out, given that anyone with
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some sense, and a desire to see these birds would just hop on a pelagic
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trip, go a billion miles out, see them in any old county and call it a day.
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But if anyone knows a little more about how these birds work, I'm curious
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to hear more. Maybe they return via undersea tunnels, sporting transparent
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plumage?
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>
I've talked to one person who has kayaked to these islands (I'm not
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kayaking to these islands), and to a fishing charter that may be willing to
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do a trip out to some of these Jeffersonian Islands. I'm just slowly trying
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to extract teeth to determine. . . How late the boat might be able to be
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out there, and how late these birds return. This may be some really easy
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math, such as: "the birds come back *after* dark" and "the boat has to
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be back before dark", but it's been a challenge to get these two numbers.
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I'm not dumb enough to even think about pursuing this if it's a purely
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nocturnal endeavor, but. . . I'm just dumb enough to get to the bottom of
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this. 50,000 birds a kayak's paddle away seems too interesting to not even
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ask!
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>
TLDR: How do Cassin's Auklets work?
>
>
Auklets aside, this goes through Tufted Puffin habitat (yes, I know where
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to find them in Island and Clallam Counties, but thank you!) - I think it'd
>
be a beautiful trip, regardless of any auklet goings-on. Feel free to reach
>
out through my blog (jkcountybirding.blogspot.com) if a trip like that
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would have your interest at all! If it feels like it would be worthwhile,
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that boat would hold six passengers.
>
>
Cheers,
>
>
Tim Brennan
>
Renton
>
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