23 August 2010

How to have a lousy time in Durham

Durham, England, famous for its grand old city and cathedral, where bus loads of senior citizens spend their day dragging their Zimmer frames over the cobbled streets to admire ye olde England. More recently and probably more famous in New Zealand, Durham's castle and cathedral might be better known as Hogwarts School of Witchcraft and Wizardry, as seen in the Harry Potter films. So, what have Lincoln University and Harry Potter got in common? Not a lot, but it sets the scene for where my current fieldwork is based.

I am in northern England to sample birds for feather lice. As you sit and scratch, feeling small legs walking through your hair, you might ask why I would travel half way around the world to do this. The source of almost all of New Zealand's introduced song birds is the UK. Sparrows, blackbirds, skylarks and finches, amongst others, were brought to New Zealand by settlers to help create a sense of home. Along with the birds came their feather parasites, although not all of the species. It is the pattern of what made it and what didn't that is of interest to us and will allow us to better think about invasive species (see this previous blog). We know how the lice are distributed around New Zealand but have only minimal knowledge about their ancestral home, especially the northern areas of England where many settler-ships left from. To model UK distributions of chewing-lice, I have been catching selected bird species and processing them for chewing lice.

While you suffer winter in NZ, I am enjoying the UK summer. I arrived in the UK in early July and quickly made arrangements to join British Trust for Ornithology (BTO) bird ringers in the field. Bird ringing (or banding) is heavily regulated in the UK and takes at least two years to gain a licence to ring birds without supervision. Naturally, this is well beyond the scope of a Masters project. This means that I am at the mercy of suitably qualified people to complete my research. All of the ringers that I work with volunteer their time and they also pay for the rings and all other costs associated with ringing birds.


More...


Apart from their natural love of birds, there are other reasons why these people ring birds: the BTO run various ringing programmes, such as The Constant Effort Sites Scheme (CES) and Retrapping Adults for Survival (RAS) that rely on data collected by these volunteers. The CES sampling protocol dictates that each site is visited once every 10 days during the breeding season (this means 11 visits). The effort at each site remains constant, i.e., the same number of nets in the same positions for the same amount of time. For example, at the Foxglove Covert CES they erect 30, 18 metre mist-nets, begin ringing at sunrise (4am in mid-summer) and remain ringing for 10 hours; whereas, at the Rainton Meadows CES they erect 8 mist-nets (a mixture of 12 and 18 metre nets) and catch birds between 7am and 1pm.

The benefit of CES for my fieldwork is that I can plan on mist-netting at least once every 10 days, weather permitting. Birds loose body heat rapidly when they get wet, so to avoid bird mortality, nets must be collapsed when it rains. Wind also affects sample effort; birds are less active in high wind and the nets become highly visible flapping about. More importantly, birds can also be injured in a moving net (e.g., broken wings and strangulation). CES sites are usually visited in the weekend, so I must decide on which to visit. Lately, I have gone where I catch the greatest number of birds, but soon, to increase the number of records for more rare species, I will have to concentrate on locations where specific bird species are caught.

This is a convenient segueway to the RAS (Retrapping Adults for Survival) scheme. Sites are selected where many individuals of targeted species will be caught for monitoring species survival rates. So far, as part of my study I have processed birds at yellowhammer, house sparrow and blackbird RAS sites. There are some species that I have few records for, so I need to find redpoll, songthrush and starling RAS sites to sample at. Which should fill the last five weeks that I am here.

While I am not delousing birds in the field, I process my samples in the lab (thanks to Biological sciences at Durham University). This entails sifting through my field samples under a dissection microscope. I have become quite tuned into finding lice floating about in a mixture of ethanol and flea powder, but it still takes about one day to process 10 samples. I have processed 135 birds (about 10% of all the birds caught at these sites) and blackbirds are by far the most lousy bird, both for prevalence and intensity.
Ok, gloves on and back to work....


No comments: