[Tweeters] How do Cassin's Auklets work?

[Stephen Elston via Tweeters]

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

> feed krill to their chicks.  In less favorable years, they switch to eating

> 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

> of the continental shelf, so they might fly considerable distances from

> their coastal nesting colonies to feed during the day.  Sometimes you see

> big feeding groups of them, likely if there is a patch of krill, but

> they’re usually more spread out.

>

> They fly back and forth to and from their colony every day, ideally not

> too far, but regularly 20-40 miles to feeding areas, often more.  A

> Cassin’s Auklet might travel 40-45 mph in fast flight depending on winds,

> so 20-40 miles doesn’t seem too far for them.  In poor feeding years they

> might have to travel much further to find food, or return smaller meal

> loads to their chicks, or else give up.

>

> They are totally nocturnal on land, other than of course during the

> nesting season when one adult stays in their burrow all day incubating

> their egg or brooding their young chick.  They leave their chick alone in

> the burrow at a fairly young age, so both parents can return food to the

> chick.  Their flights ashore to nesting islands occur well after dark, as

> they are sensitive to light levels even at night.  Because of predation,

> they are slow to come onshore during moon-lit nights, but on dark moonless

> nights they come ashore right away.  Sometimes they all come ashore in a

> giant wave, and sometimes they trickle in over a long period.  They seem to

> be able to locate things fairly well even on dark nights, so they must have

> excellent night vision.  Most departures in the morning occur well before

> dawn, but there are sometimes late departures that may end up in the belly

> of a gull or a Peregrine Falcon.

>

> When flying ashore, they usually fly in very quickly, plop down, get their

> bearings, and quickly make their way to their burrows.  They often collide

> with things on their way, including people, but almost always they quickly

> shake it off and keep going. They do everything they can to avoid predation

> by gulls, which nest nearby and lurk in the auklet colonies at night. The

> auklets dig their own burrows or else nest in rock piles or rock cavities.

> Most burrows are about 2 to 4 ft deep, so once inside predators hopefully

> can’t get to them.  Breeding pairs are very faithful to their burrows

> between years.

>

> Cassin’s Auklet adults have a nifty sublingual (under-tongue) pouch they

> use to carry prey to their chicks.  The consistency of the goo they carry

> in their sub-lingual pouch is kind of like shrimp cocktail, which they lap

> out to the chicks when they reach the burrows.  Meal loads with krill are

> mostly pink because of their photophores, whereas meal loads with fish are

> mostly gray fish chyme.  We randomly captured auklets flying in with

> pouches full of food and sampled their pouch contents. It’s quite amazing

> how large their meal loads can be relative to the size of the bird — a

> 180-200 g adult sometimes carried a 40-50 g meal load, or about 1/4 of

> their body weight.  They can cram a lot of krill and larval fish into their

> bulging sub-lingual pouch.

>

> Unfortunately many Cassin’s Auklet populations have been shrinking,

> between marine heat waves, El Ninos, predation, and who knows what.  The

> 50,000 auklets estimated nesting on Alexander Island by Speich and Wahl in

> the 1970s might be much smaller now.  But realistically, how do you

> estimate the numbers of a small seabird that only comes ashore at night on

> remote islands and then nests out-of-sight in underground burrows?  It’s a

> shot in the dark — ha ha!

>

> The best thing about Cassin’s Auklets is their singing — imagine thousands

> of them chirping away on a windswept island in the middle of the night.

> They scream their three-note songs while sitting in their burrows,

> repeating things like “LET ME OUT, LET ME OUT, LET ME OUT” and “IT’S ALL

> 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

> most recently made a trip to the coast, adding 8 more birds to the year

> list. This included some Black Swifts over a meadow behind a gift shop on

> the way up to the Hoh, and a few stray pelicans. 169 for the year in

> Jefferson was a Common Nighthawk over a clear cut (clearcut? Clear-cut?)

> off of FR-3000 the other night.

>

> The goal is two hundred species for the year. My bet is that I'll come up

> a little short of that, but have a great time trying. One thing that has

> been eluding me is some open-minded conversations about seabirds, and maybe

> more specifically, I am trying to understand Cassin's Auklets. A couple

> things I do understand about them. They are usually seen very far out from

> shore. Yep. The pelagic trips from westport head out far enough, but not

> into Jefferson. Repositioning cruises pass through Jefferson waters, but

> they pass through a lot of other waters, to my understanding, and might be

> 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

> or so Cassin's Auklets nest on Alexander Island, Jefferson County. And this

> is like... A mile off shore. They go out far. I understand this. 😄 But...

> Then they come back, yes? Is their return usually in full dark? Late in the

> day? It may be information that's hard to pull out, given that anyone with

> some sense, and a desire to see these birds would just hop on a pelagic

> trip, go a billion miles out, see them in any old county and call it a day.

> But if anyone knows a little more about how these birds work, I'm curious

> to hear more. Maybe they return via undersea tunnels, sporting transparent

> plumage?

>

> I've talked to one person who has kayaked to these islands (I'm not

> kayaking to these islands), and to a fishing charter that may be willing to

> do a trip out to some of these Jeffersonian Islands. I'm just slowly trying

> to extract teeth to determine. . . How late the boat might be able to be

> out there, and how late these birds return. This may be some really easy

> math, such as: "the birds come back *after*​ dark" and "the boat has to

> be back before dark", but it's been a challenge to get these two numbers.

> I'm not dumb enough to even think about pursuing this if it's a purely

> nocturnal endeavor, but. . . I'm just dumb enough to get to the bottom of

> this. 50,000 birds a kayak's paddle away seems too interesting to not even

> ask!

>

> TLDR: How do Cassin's Auklets work?

>

> Auklets aside, this goes through Tufted Puffin habitat (yes, I know where

> 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

> would have your interest at all! If it feels like it would be worthwhile,

> that boat would hold six passengers.

>

> Cheers,

>

> Tim Brennan

> Renton

> _______________________________________________

> Tweeters mailing list

> Tweeters at u.washington.edu

> http://mailman11.u.washington.edu/mailman/listinfo/tweeters

>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman11.u.washington.edu/pipermail/tweeters/attachments/20240617/b38af218/attachment.html>