Migration of "non migratory" species

[Chuck]

In an email, John Calhoun made mention of Papilio glaucus "migrating" north during the summer in US northeast.

Recently, Harry Pavulaan made mention of Papilio glaucus "migrating" from valleys to mountain tops during summers in the Skyline (VA) area.

I usually think of "migrate" as permanent, though obviously that is not inferred by the definition. So I suppose the above use of the word is correct.

What other species migrate temporarily, perhaps with offspring not surviving?

We discussed Vanessa atlanta apparently migrating north during 2024, in huge numbers. viewtopic.php?p=10205&hilit=vanessa#p10205

And, observations from 2024 of Papilio cresphontes appearing in way northern NY and Ontario CA. viewtopic.php?p=10879&hilit=cresphontes#p10879 I wonder- was this a localized population explosion, or was it migration from the south? If it was migration, from where did they come?

What are the ramifications of temporary migration where closely related taxa might overlap? Not really thinking this through, in the case of migration to colder (northern or higher altitude) it would probably be minimal since hybrid offspring won't survive.

A recent publication in LepSoc pointed out that Danaus gilippus is indeed migratory, despite long-held beliefs and lack of study / interest.

How long does a move have to last in order to be considered "migration"? An observation of MST in our area is that many of the adults come from somewhere to my primary research hill to nectar, and then return at the end of the day. I know they're coming from the south west, but I don't know if they are travelling 0.5km or 20km. This I'd not consider "migration" but does bring up another question- how far will a Lep fly to nectar?

Anyone have thoughts or observations on unpublished or undiscussed "migration"?

[Jshuey]

This is a common mis-use of the term migration". Most people use it in two ways. To describe "round trip" movements - like migratory birds or monarchs in North America, or movements that establish new homes, like a lot Europeans migrated to North America over the past couple hundred years. In both cases there is a general directional movement and it is adaptive - as in it allows successful migrants to thrive.

It is also being used in conservation - "assisted migration". We just moved a bunch of Franklin's ground squirrels into Indiana in an attempt to establish a population that can weather future predicted climates. The idea that you can move certain species northward to save them. We have been moving seeds from some types of southern oaks into Indiana for years in an attempt to introduce "southern genotypes" into our populations of black, white and other oaks - just to hopefully give these key tree species the genetic diversity they may need for the future. In this case, the species are already here, we just want them to have access to southern genes - just in case they need them in a few decades.

But people also call dispersal that accomplishes none of these things as migration. Like all those southern butterflies that wander northward in the US every year, only to get killed back in the winter. This is probably the result of random movement in all directions, such that we only see them when the wander into new regions (and don't notice those individuals that simply mingled within their normal range). I always try and differentiate between migration and dispersal when I use the terms - but not many other people make this attempt.

As to moving back and forth between habitats in the search for resources, that is more of a "home range" issue. Rare Skippers (Atrytone byssus) are well known for spending the day out in hard to access salt marshes, but early in the morning, come inland to seek nectar. Turns out that they are not that rare - you just have to know when and where to look for them.

John

[Chuck]

^^ and that's why this forum is so cool.

[kevinkk]

this forum is so cool.

Exactly. I see the word "migration" typically as something seasonal, when it comes to animals. We see it every year when geese fly overhead.
I would think there is probably a better term for "permanent migration" which wouldn't really be migration, it would be relocation or "moving".
Maybe a linguist would sort it out, maybe it's simply a multi purpose term which needs context to be defined.
Animals flee all kinds of climatic conditions, even seagulls "migrate" inland before storms, and some insects flee hot weather for the mountains.

[JVCalhoun]

A quick comment: I actually wasn't the source of the remark about the "migration" of glaucus in the northeastern US. Chuck and I recently emailed quite a bit about this group of butterflies, and he made an honest mistake. I agree with John Shuey's assessment, and think that glaucus simply disperses northward from its permanent range.