Whats wrong with the golden orioles?

[kiwi]

Theres only 5-17 pairs in the UK and they're on the red list, yet i can't find out why they're so low on numbers.
Any help?

Thanks

[RoyW]

A lot of the rarer breeding birds in Britain are right on the edge of the species range (Golden Orioles included). Unless these species increase their population in the main part of their range, forcing some to find breeding territories elswhere, they will probably never become common in this country.
Some may also be limited by factors such as climate, food availability, and a reluctance to cross open sea (the channel).

Roy.

[Adam Cheeseman]

Plus they are a relatively new breeding species here preferring mature poplar forest, which is not a particularly common habitat here.

Cheers,

Adam

[kiwi]

Oh i see thankyou

[Picidae]

Seeing as they are long distant migrants (winter in sub sahara) not sure a reluctance to cross open water is such an issue. However, as Adam indicates, in the northern extreme of their range, they are reliant on Popular plantations, of which we have relatively few in the UK. They are very widespread and common in continental Europe but the further south you go, the more diverse the breeding habitat (mixed deciduous woodland, parks and gardens). The real issue is, as Roy says, that they are on the edge of their breeding range in the UK. I suspect it's the population size that restricts the diversity of habitat rather than the other way round - the further to the extra-limital boundary of any species of bird, the fewer breeding pairs there are to sustain a sizeable population and they are more likely to be concentrated in a smaller area. Climate change ie. earlier and warmer spring may benefit early migrants such as Orioles (mid April in Southern Europe) and we may see a gradual expansion North. Planting of Black Populars (which bud earlier) could also encourage expansion Oriole in UK in the future.

[kiwi]

Then why would they be on red list and not green list if its not down to population decline?

[Picidae]

Originally Posted by kiwi

Then why would they be on red list and not green list if its not down to population decline?

That's actually a complicated question if you do not understand the ICUN system of categorisation! I'll try and explain.

First thing to note is that Global catergorisation of a taxon (species) may be different from a Regional or Local catergorisation of that same taxon. THUS, a taxon may be of Least Concern globally but might be catergorised as 'Critically Endangered', 'Threatened with Extinction' etc on a Regional or Local level within a particular area where numbers are small (or declining) because they are at the edge of the margin of their global range (As with GO's in UK).

Second thing to note with regard to the ICUN system of Red Listing is that there are 5 criteria, any of which may be satisfied (with supporting evidence, including projection in inferrence ie. forecast) to categorise a taxon as a Red Listed species.

With regard to Golden Oriole in the UK:

Under the ICUN catergorisation system, factors related to population abundance and or distribution provide the supporting evidence needed to make Golden Oriole at risk of extinction in the UK, ie Golden Orioles are on the margins of the global range for this taxon - thus, projection/inference of the risk of extinction due to population size, puts GO on the Red List in the UK per se, simply because the breeding population here is so small.

It's a complicated system and has been subject to many reviews but that's best how I can explain the current method of Red Listing and how it applies to Golden Oriole in the UK

[RoyW]

Originally Posted by RoyW

Some may also be limited by factors such as climate, food availability, and a reluctance to cross open sea (the channel).

Originally Posted by Picidae

Seeing as they are long distant migrants (winter in sub sahara) not sure a reluctance to cross open water is such an issue.

Not the best example for me to have used when the bird under discussion was Golden Oriole - this was meant as a more general comment and may be a reason why other species, which can be found across the channel, do not regularly breed in Britain - Serin for example.

I agree with the comments regarding habitat - Golden Orioles do use other habitats, and have apparently previously bred in Oak/ Sweet Chestnut in Britain.

Roy.

[kiwi]

Thank you for explaining
So it's not that they're declining its that population is so small it's on the verge of extinction in the Uk