Indoor Post

Looks like I won’t get out birding or ringing for a few more days. To put it mildly, the weather is crap by way of the usual wet and wind. 

But hopefully 2018/19 may turn out to be a “Brambling Winter”, an irruption year for this close relative of the much more common Chaffinch. Migration watch points and Bird Observatories are reporting abnormally large numbers of Bramblings when in more typical years the numbers of Bramblings seen is low in comparison to other autumn migrants and to species that overwinter. 

Trektellen shows a clear spike in UK numbers in late October early November 2018 with three or more days of 2000+ Bramblings at Hunstanton Cliffs, Norfolk and at Spurn Bird Observatory. There are also several days of counts in the high hundreds. 

Brambling 2018 - https://www.trektellen.nl

Brambling 

Brambling 

However, sightings here on the west coast are not nearly as high which is not unusual given that the range of the Brambling is biased towards the east by stretching from Scandinavia and then east through an enormous swath of taiga forest across to Sakhalin and Kamchatka. This area is at the most extreme eastern edge of the Russian Federation at the Pacific Ocean and very close to the northern tip of Japan. 

In "Brambling winters" it is often into the extremes of January and February and icy temperatures before Bramblings find their way to the warmer west coast of England. Such irruptions in a number of birds of Northern Europe most often involve species like Hawfinch, Brambling, Chaffinch, Waxwing, Bullfinch, Siskin, Coal Tit and Crossbill. The common factor is each species’ reliance upon the various seeds of trees found in northern taiga, also known as boreal forest. 

Crossbill 

Waxwing 

These irregular migrations are difficult to study because it is hard to predict when they will happen or where the birds will go each year. In each case, however, irruptions follow some type of boom-and-bust cycle of food sources. It is important to note that many winter birds will gather in flocks for the season, but that does not mean they are irrupting. An irruption is characterized by a distinct shift in the birds' typical winter range, with many birds appearing well outside the normal boundaries of their winter homes. 

Waxwing

The most common cause of this phenomenon is called “masting,” which occurs when a single tree species produces a large number of seeds across thousands of miles of forest in the same year. When the conifers in the boreal forests of Northern Europe experience a masting year, the abundance of seeds gives some species of bird a boost. The birds begin breeding earlier than usual and produce more offspring, resulting in a population boom. When autumn arrives, the bird population has doubled or even tripled, but the available habitat hasn't. Many birds move south, and young birds in particular may be pushed further and farther south and west in search of both food and somewhere to spend the winter. 

Other causes for bird irruptions include unduly harsh cold or severe weather that may force birds to find more temperate wintering grounds, or over-breeding that may deplete even plentiful food supplies. No matter what the cause of the irruption, however, it is difficult to predict where or when irrupting species may appear.

It is known that the Brambling’s strategy during winter, to roost in large dense flocks, is superior to those of other passerines. Also during summer Brambling densities can be very high even at breeding sites when food is abundant. Thus the Bramblings seem to prefer wintering in flocks as large as the available food supply allows permits. 

This may explain why flocks estimated at between 2 million and 5 million Bramblings are sometimes recorded in Scandinavia, Central Europe and Japan. Such flocks can even occur in good years for beech mast, a favoured food of the Brambling. 

Take a look at the video below. At first glance it appears to be a video of a murmuration of Starlings, but in fact all of the birds are Bramblings. The video was shot in Japan, sometime during the winter of 2015/16.  

Back soon with an outdoor post. Until them linking this post to Anni's Blog and Eileen's Saturday.