Continental Blackbird?

[Cordaline]

Is this a Continental Blackbird please?

[david156]

Hi,

From the shape I would agree its a blackbird but from where is hard to say. This country does get lots of continental Blackbirds in the winter and judging by the number of Waxwings that have come over here from scandinavia I would be inclined to say a lot more than usual numbers of Blackbirds have probably headed over this way too.

What made you enquire whether it was from the continent? Was it behaving in an usual manner?

Cheers David.

[Acipiter]

Don't continental birds have black bills?.

[Picidae]

Originally Posted by Acipiter

Don't continental birds have black bills?.

All first winter male blackbirds have black/dark bills and dark eye rings - which this is.

No difference between continental and resident birds - they are the same race

[Dogghound]

Without having my head bitten off! Have continental birds ever been studied? is there any papers/books. Its something I find really interesting. We only get blackbirds with blackbills and black eye rings after autumn falls on the east coast. The resident birds tend to be a lot brighter in bill and eye ring. Obviously I ring a lot of these birds so you can see there is a clear size difference aswell with northern birds being larger. Just a coincidence?

P.S im not interested in an argument I simply want to know

[faz]

as far as i understand most of the black billed black birds are from the contianent ? all the ones in my garden are i have seen, all the fledings from this year cant say as they have gone to pastures new

[Picidae]

Originally Posted by Dogghound

We only get blackbirds with blackbills and black eye rings after autumn falls on the east coast. The resident birds tend to be a lot brighter in bill and eye ring.

Once our resident birds have completed their post juv moult, they retain dark bills/eye rings throughout the winter. Therefore, it's not surprising that they are seen during the autumn as ''adults'' but with dark bills and some retained brown juv feathers.

There is a southerly movement in Autumn of residential birds so those moving down the east coast could well be coming from northern Scotland/England - The only reliable way to ascertain where our winter blackbirds are from are by ringing recoveries. ''Ringing recoveries have demonstrated that we receive autumn Blackbirds from Scandinavia, Estonia and Germany (Kerr, 2001)'' http://www.ntbc.org.uk/Visible%20mig...udle%20Bay.pdf

It's also worth reiterating that the bill and eye ring colour of our first winter blackbirds is primarily due to AGE and moult development and not due to subspecies/racial separation. I think it's many of these type that people are jumping to conclusions with about their derivation. Additionally, both adult continental birds and resident birds will have darker bills in winter than in breeding season.

The colour of bills/eyerings is related to hormonal conditions (underpinning the age/moult causation of bill colour change) which in turn is precipitated or delayed as a result of diet/food availability/climate and light. You may find this article very interesting and sort of explains why the same sub species of bird may vary in it's bare parts colour cf. to it's counterpart at the same time of year, depending on it's breeding grounds.

It also might support an argument for differentiations between forest breeding continental Blackbirds and our more urbanised residents:

http://www.ncbi.nlm.nih.gov/pmc/arti...f/15451688.pdf

[Dogghound]

Thankyou Picidae.

Additionally the birds we get are usually as part of falls which include norwegen and swedish ringed birds. They often comprise of lots of other birds with large wing lengths such as goldfinch as well as brambling and redwing, which suggests northern europe. Its probably safe to assume they are continental. We do get british birds with smaller wing lengths moving down the coast predominantly during northerly winds, we had decent numbers of greenfinch earlier this autumn.

[Picidae]

Originally Posted by Dogghound

Thankyou Picidae.

Additionally the birds we get are usually as part of falls which include norwegen and swedish ringed birds. They often comprise of lots of other birds with large wing lengths such as goldfinch as well as brambling and redwing, which suggests northern europe. Its probably safe to assume they are continental. We do get british birds with smaller wing lengths moving down the coast predominantly during northerly winds, we had decent numbers of greenfinch earlier this autumn.

Wing morphology can also be age related - as with the bare parts colour of wintering Blackbirds - not that I question the validity of using wing length as an indication of migration habit in passerines (longer wings, more pointed primaries, shorter tails, in reducing migration cost), just that there's also focused ringing studies on specific species that have shown there are variables that need to be taken into consideration before extrapolating assumptions about derivation of unringed netted birds (ie. a ring to show it was ringed as a 1cy bird in it's country of origin and recovered in the UK during the winter period) - which is probably the sort of study you were wanting to source. With species that don't breed in the UK (or not as a rule) assumptions about 'autumn falls' being non resident birds are probably better placed and certainly ring recoveries will confirm country of origin if the bird is aged correctly when recovered and thus shown to have been ringed in it's first year.

Re: Wing morphology irt to migration: In some passerines, ''studies have found that wing length or pointedness is not correlated with migration distance or migratory behavior (Keast 1980; Mulvihill and Chandler 1990, 1991; Burns 2003). These results may occur because avian flight apparatus is also shaped by other, potentially opposing, selection pressures. For example, predation may select for shorter rounder wings that improve take-off performance (Norberg 1990, Swaddle and Lockwood 2003), and shorter rounder wings and longer tails that enhance maneuverability (Norberg 1990). This may explain why juvenile birds, which are more vulnerable to predators, typically have shorter and more rounded wings than adults (Alatalo et al. 1984). Avian flight apparatus may also be shaped by use of differing foraging strategies, habitat selection, prey size, or sexually selected courtship behaviors (Norberg 1979, Winkler and Leisler 1985, Hedenstro¨m and Mo¨ller 1992''


The above, combined with the previous article I linked to on studies cf. urban and rural populations may be another basis for question the use of wing morphology in ascertaining migratory distance: Shorter rounded wings make for better manoevrability, (migratory populations develop longer pointy wings which plays off against reduced maneovrability) therefore given that 'wing morphology can evolve rapidly' over a period of a few generations, I would like to see comparative ringing studies between our resident urban 'v' rural Blackbirds populations too (and over a period of several years and during the winter months to ensure accurate wing morphology in fresh plumage) to see whether urban predation (where cat/Sparrowhawk predation can be intense in a relatively smaller area cf. to rural/forested habitats, along with the need to routinely navigate a tightly built up urbanised environment has any effect on suppressing that development in rural/forest breeding residential populations of Blackbirds (and other wintering visitors from Scandinavia/Russia/Poland etc) and whether birds moving south during the autumn migration showing variation in wing morphology, do so because of the nature of their breeding habitat and age rather than migratory distances.

There are also studies that have shown city breeders are less likely to move during winter months than those breeding in rural areas due to micro climate and food availability - thus, fall movements are more likely to be consisting of rural populations anyway.

http://www.sfu.ca/biology/wildberg/p...netalWJO09.pdf

On the same note, our migrant wintering Blackcaps from Germany replacing our long distance uk residents which fly to Africa, 'should' show a shorter wing length in adults than our UK ones - however, given the German influxes are from populations breeding in the Black Forest (amongst other rural areas) it would be interesting to see how that played out in wing length vis a vis cf. breeding habitat variation.

I guess to conclude, in my opinion no presumptions can be made without solid ringing data and using that data to compare age and breeding ecology/habitat of those that have been ringed and recovered amongst residential populations from both rural and urban breeding habitats.

All interesting stuff though!! More CE ringing studies of Scottish/NE residential birds would be helpful along with a comparison of city dwelling residents.

[Picidae]

Sorry above paragraph should read as italicised:

''I would like to see comparative ringing studies between our resident urban 'v' rural Blackbirds populations too (and over a period of several years and during the winter months to ensure accurate wing morphology in fresh plumage) to see whether urban predation (where cat/Sparrowhawk predation can be intense in a relatively smaller area cf. to rural/forested habitats), along with the need to routinely navigate a tightly built up urbanised environment has any effect on suppressing that development in urban populations cf to rural/forest breeding residential populations of Blackbirds (and other wintering visitors from Scandinavia/Russia/Poland etc) ''