Wikipedia:Reference desk/Archives/Miscellaneous/2023 December 30

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December 30

Two colors of bald eagles?

I know bald eagles are dark brown, but in some photos, they appear black (I'm not talking about the juveniles. in the photos I'm taking about, they're black with a white head and tail like adults). EAGLITIZED (talk) 16:45, 30 December 2023 (UTC)

Lighting.--User:Khajidha (talk) (contributions) 17:30, 30 December 2023 (UTC)

As with the varying apparent colors in illustrations within Bald eagle. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:25, 30 December 2023 (UTC)

Irish golden eagles

I know it's strange to ask this question, but I heard there were sightings of golden eagles in Ireland, and I was just wondering which cities, towns, villages etc. they were found in EAGLITIZED (talk) 16:49, 30 December 2023 (UTC)

According to [1] and [2], it was reintroduced in County Donegal. --Wrongfilter (talk) 17:00, 30 December 2023 (UTC)

Was the golden eagle really reintroduced to Ireland, I thought there were only sightings people didn't know about. 2600:6C44:627F:5865:D028:C3FF:FE4B:8D02 (talk) 18:55, 31 December 2023 (UTC)

Do those web sites not look legit to you or do you have any other reason to doubt what they say? --Wrongfilter (talk) 19:18, 31 December 2023 (UTC)

I didn't doubt any websites, This is the first time I learned golden eagles were reintroduced and I just got confused... 2600:6C44:627F:5865:D028:C3FF:FE4B:8D02 (talk) 18:19, 1 January 2024 (UTC)

Subspecies of white-tailed-sea-eagles

An article on Wikipedia said that there are two subspecies of white tailed sea eagles, but there are no photos that compare them. I need all the information on the differences of the two subspecies. EAGLITIZED (talk) 16:59, 30 December 2023 (UTC)

From ourown article: "At one time an eastern subspecies (H. a. brooksi) was proposed as well but there is little evidence supporting this as more than a case of clinal variation in colouring and size (i.e. the eastern average slightly darker and smaller than more westerly ones)." Basically, the division into two subspecies isn't certain and, even if it were, it wouldn't necessarily be evident from photos.--User:Khajidha (talk) (contributions) 17:29, 30 December 2023 (UTC)

Texan stellers sea eagles, and Irish bald eagles, I don't think so!

I learned a stellers sea eagle wound up in Texas after a snow storm. Texas isn't even close to Asia where they normally live. I also know bald eagles have crossed the Atlantic Ocean and wound up in Ireland. How does a bird fly that far? EAGLITIZED (talk) 17:21, 30 December 2023 (UTC)

"How does a bird fly that far?" See Arctic tern for an example of a bird where this is a built-in feature, not an accident. So, yes, birds can fly an awful long way. Xuxl (talk) 18:25, 30 December 2023 (UTC)

The record holder so far is the bar-tailed godwit. "The migration of the subspecies Limosa lapponica baueri across the Pacific Ocean from Alaska to New Zealand is the longest known non-stop flight of any bird, and also the longest journey without pausing to feed by any animal" according to our article. One individual flew non-stop from Alaska to Tasmania, Australia, a distance of 13,560 kilometres (8,430 mi) in just over 11 days reported here by the Guardian. Mikenorton (talk) 21:53, 30 December 2023 (UTC)

By flapping its wings.

Taking r the lift-to-drag ratio of the bird's wing, g the acceleration of gravity, H the energy released by burning a certain amount of fat and k the efficiency at which this energy can be used for propulsion, and realising that work needed equals trust times distance, that trust equals weight divided by lift-to-drag ratio and that its mass decreases as it burns its fat, it's trivial to find the differential equation relating mass m to distance covered s:

${\frac {dm}{ds}}=-{\frac {mg}{rkH}}$

which leads to

$m(s)=A\exp(-{\frac {gs}{rkH}})$

Filling in some plausible numbers (r=14, k=0.2, H=3.8⋅10⁷ J/kg), this tells us that a bird can fly 13,560 km without foraging if it's able to burn an amount of fat equal to about 70% of its initial body weight. If the bird encounters convenient winds, in particular rising air, it may need less fat. It's pushing the limits of what's biologically possible, but it's no magic. PiusImpavidus (talk) 14:08, 31 December 2023 (UTC)

Re-reading my copy of A world on the wing by Scott Weidensaul (ISBN 978-1-5098-4105-9) it says on page 66 that they do this by feeding up prior to departure from Alaska in September, more than doubling their weight, giving them thick layers of fat. Their "gizzard and intestines shrink and atrophy, while their pectoral muscles double in mass....as does their heart muscle, and their lungs increase in capacity". They make use of favourable autumn tailwinds to give them a headstart for the first part of their trek, powering on until they reach the austral westerlies that give them a final boost. They do it all again twice in the spring, travelling back to Alaska via a stopover in China/Korea. Mikenorton (talk) 15:45, 31 December 2023 (UTC)

This autumn, the fall migration along the eastern seaboard of North America was interrupted by Hurricane Lee, causing large numbers of American birds to turn up unexpectedly along the west coasts of England, Ireland and Scotland, driving the local birders wild with excitement, see another Guardian article. Mikenorton (talk) 15:57, 31 December 2023 (UTC)

The range map in our article is pretty poor, but it seems to indicate that, if Alaska existed, it would fall within this species' "vagrant range". Going from Alaska to Texas is a fair jump, but it's not like they're coming from Iraq or something. Matt Deres (talk) 00:24, 2 January 2024 (UTC)