Species reshuffling and climate change

[Julie]

I found this thread interesting and it got me to thinking...as a new Texas member of the communitysurfbirds, I'm interested in migration from the south, as well as climate change effect. We have an urban heronry here in Dallas, smack dab in the center of the large medical center I work in with perhaps 2,000 nests (anhingas; white, black-crowned night-, little blue, and tricolored herons, cattle egrets) and I wonder if it thrives in part due to habitat destruction along the Texas coast??? It has been there about 50 years, reportedly. I am doing some informal research regarding urban heronries and am trying to determine longevity, reasons for heronry destruction vs. abandonment, etc.

Perhaps this is not consistent with this thread, but as there is so much birding expertise on this site and I am relatively new to birding, does anyone have any thoughts to share regarding climate change and east-west vs south-north migration patterns? Do those of you with years of experience have a sense of climate effect changes?

An article that may be of interest regarding California migration follows:
Re-Shuffling of Species with Climate Disruption: A No-Analog Future for California Birds?

www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0006825

(not sure how to post a hyperlink here)

I apologize for my non-linear train of thought.

Julie

[AndyB]

Hi Julie, we made this its own thread. There seems to have recently been an increase in Reddish Egret sightings in southern California (they're a vagrant here) and also Arizona (where the population is expanding). The origin of these birds appears to be west Mexico.

Over in the UK, Little Egrets have become quite common in southern England where they were a regular vagrant less than 30 years ago. They now breed and Cattle Egret has recently bred for the first time too. Currently there are small flocks of Glossy Ibis touring the country. These are all herons of southern Europe that rarely ventured across the English Channel.

I guess herons are doing OK in the current climate.

[mafting]

Over in the UK, Little Egrets have become quite common in southern England where they were a regular vagrant less than 30 years ago. They now breed and Cattle Egret has recently bred for the first time too. Currently there are small flocks of Glossy Ibis touring the country. These are all herons of southern Europe that rarely ventured across the English Channel.
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Although there are other potential explanations for this aside from climate change. Fulmar and Collared Dove radically changed their distribution for no clear reason a century ago.

The herons might be colonising Britain due to population pressure just over the continent, where conditions over the past 30 years have never been better: abundant new habitat, high protection and low persecution, and eradication of the worst pollution. All of that is independent of climate.

If the herons were responding solely to climate, then why aren't Little Bittern, Great White Egret, Spoonbill and Purple Heron responding in the same way? It's a more complicated question than it first appears.

[AndyB]

Yes, I agree.

For instance, Collared Dove's expansion north and west even across the Atlantic can't be blamed on climate change. By the way, they expanded beyond the west coast and can now occasionally be seen on islands off California now.

[MichaelF]

Little Egret isn't responding to climate change, it is just re-occupying former range from which it became extinct due to excessive hunting; probably the same applies to other herons, which all suffered very heavily from persecution for food, as perceived competitors for fish, and for plume feathers.

I'd not be at all surprised if the same applied in Dallas, where it is more difficult for illegal shooting of herons by disaffected fishermen in urban areas than it is in remote rural locations where wildlife crime is much less easy to detect.

[mafting]

Little Egret isn't responding to climate change, it is just re-occupying former range from which it became extinct due to excessive hunting; probably the same applies to other herons, which all suffered very heavily from persecution for food, as perceived competitors for fish, and for plume feathers.

I'd not be at all surprised if the same applied in Dallas, where it is more difficult for illegal shooting of herons by disaffected fishermen in urban areas than it is in remote rural locations where wildlife crime is much less easy to detect.

What's your evidence for Little Egret breeding in Britain in the Holocene? And why weren't Grey Herons affected in the same way?

AndyB - didn't Collared Dove get across the Atlantic via man? I thought the US population was thought to have originated from escapees from the Bahamas getting to Florida?

[MichaelF]

What's your evidence for Little Egret breeding in Britain

See e.g. Brit. Birds 96: 332-339 (2003).

Grey Herons often breed in much less accessible locations, and less conspicuously, so wouldn't have been so easily hunted out.

[Colin Key]

.... didn't Collared Dove get across the Atlantic via man?

If you could give me the name of this man mafting I will go and shoot him. I have 200+ roosting in trees on my land - apart from their bloody awful noise their s**t is killing my grass and plants.

Colin :realmad:

[mafting]

See e.g. Brit. Birds 96: 332-339 (2003).

Grey Herons often breed in much less accessible locations, and less conspicuously, so wouldn't have been so easily hunted out.

Hmmmn, on reading that I'm very sceptical of the conclusions. He gives no evidence that they weren't imported (as many fowl were), and doesn;t explore this, and does not back it up with sub fossils or bones (of which you'd expect lots if they were in the Fens, e.g. Flag Fen, or commonly eaten in albeit diminishing numbers). The painting from east Anglia shows a parrot next to the egret, so that's hardly proof of much (except an exotic menagerie?)!

Of course, a counter argument is that little egrets ARE influenced by climate, and colonised during the Medieval Warm Period, and then disappeared at the Little Ice Age, and are now recolonising due to warming again. That would certainly fit a narrative.

Re Grey Herons being less easy to hunt out, Bitterns were thought to have been partly hunted out (along with drainage), so if hunting can affect them then herons will be a doddle! (can't see how they're less conspicuous than egrets - same colonial nesting, same racket and smell, and they're bigger to boot).

Colin, are these doves of yours in Portugal? If so, they got there purely under their own steam!

[Colin Key]

Colin, are these doves of yours in Portugal? If so, they got there purely under their own steam!

Yes mafting, they are in Portugal and mostly in my garden, but where did they come from originally?

In "Breeding Birds of the Algarve" (Vowles & Vowles, 1994, Pub: Centro de Estudos Ornithológicos no Algarve) this species was only referred to in Appendix I (p.347): "Breeding was suspected near Messines and near Burgau during the course of fieldwork for BBA, but no proof was obtained. Since the completion of this work, breeding has been proved near Sagres".

My first visits to the Algarve were in the late 1980's and this species did not exist (as far as my own observations were concerned) - now it has almost epidemic status and breeds all year round (I have been told that they can produce eight broods a year).

It is that incessant call which I hate; next time you hear it listen carefully to what they are saying: "You bastard, you bastard, ........".

Colin :ohdear:

[MichaelF]

Bitterns were thought to have been partly hunted out (along with drainage)Drainage is by far the more significant factor here!
herons will be a doddle! (can't see how they're less conspicuous than egrets - same colonial nesting, same racket and smell, and they're bigger to boot)Much wider breeding range, including areas with very low human population density (e.g. western Scotland) where they could thrive with minimal disturbance, and recolonise rapidly whenever hunting pressure dropped in England.
they [Collared Doves] are in Portugal and mostly in my garden, but where did they come from originally?India, before the great expansion westward started. If you want to get away from them, try up here - they're decidedly scarce here. But you'll have to put up with Wood Pigeons instead :laugh:

[mafting]

Drainage is by far the more significant factor here!

Agreed, although hunting was apparently widespread. Worth remembering that many marshes were 'worked' until recently - fowlers, eel-catchers, etc.

Much wider breeding range, including areas with very low human population density (e.g. western Scotland) where they could thrive with minimal disturbance, and recolonise rapidly whenever hunting pressure dropped in England.

But population was much higher in W Scotland back then....if they managed to wipe out wolves, beavers and most of the native forest, then heronries would have been obvious and easy I'd have thought.

India, before the great expansion westward started. If you want to get away from them, try up here - they're decidedly scarce here. But you'll have to put up with Wood Pigeons instead :laugh:

Indeed, don't quite get Colin's point here - they could have walked to his gaff if they wanted to! They originated in Asia, spread into the Balkans by around the 20s, and then colonised the rest of Europe at a rapid rate. In the US, they escaped/released in Bahamas in the 70s, then spread to Florida by the 80s, and then marched westwards and are now at the Pacific. Unless his birds are African Collared Doves?