As the breeding season draws to an end, it’s time for us to complete our bird territory survey maps. These are the surveys we carried out from mid April to the end of June – it feels a long time ago now. I mentioned the theory behind the surveys in a past blog if you need to check back. The next stage involves transferring records from our working copies onto a fresh map, concentrating on each species in turn - bear with me through the following explanation! For example, every robin record is drawn onto one map, so we can see where the clusters of robin records are over the course of the surveys. Every individual survey is assigned a letter (eg first visit = Visit A) and instead of using the BTO code for robin on these new maps, you record the visit letter along with the ‘behaviour’, eg was it singing (a circled letter), alarm calling (an underlined letter) or carrying food (‘with food’ noted alongside). Sounds confusing so below is a photo of my robin map for Brandon Fen – hopefully you can read my handwriting and locate where robins were seen ‘with food’ (visits D,G and H) and also when I spotted some juveniles during visit H.
Photo credit: Ali Blaney – Robin territory map of Brandon Fen 2013
Happily my robin map shows some distinct clusters and I’m pretty happy that I located five robin territories in my area of Brandon Fen. Although a couple of the clusters seem quite close, particularly the two toward the south-eastern corner, the dotted lines between birds in visits C and H denote two different birds singing at the same time, so definitely two territories. With the robin map sorted it’s time to deal with the blackbird, the chaffinch and blackcap etc. If you can spot in advance that two species occupy different habitat areas on your map, then in the interests of being thrifty you can fit more than one species onto a single map. In my case the blackbirds were more prominent in the areas around the car park and visitor centre while the blackcaps preferred the elder along the entrance track and around the middle of the new trail up onto the riverbank, so these two species shared a map.
Analysing the clusters takes a bit of concentration, as there are certain requirements that must be met for the cluster to actually translate into a breeding territory. For example there must be ten full days between the first and last record in that cluster, which shows a bird was present for a certain length of time. Records linked by a dotted line, indicating two birds singing at the same time on the same visit, should not be included in the same cluster, while a solid line indicating the same bird moving to a different perch should not be treated as two separate territories. The easiest thing to do is to spot a nest with eggs or young in it, as that single record is accepted as being the basis of a cluster. Not always easy to do though! I was fairly lucky in Brandon Fen as we have nest boxes dotted around so keeping an eye and ear on the activity happening around those is certainly do-able. I was also excited to pinpoint the location of a dunnock nest by observing the adults behaviour, I then worried about it in between visits – ground-nesting birds seem so vulnerable!
Going back over the survey maps really takes you back to those lovely early mornings and the notes along the edges help recall what happened in each. Marvelling during the early surveys at how many siskin were still about, watching a muntjac barking ferociously at a fox (the fox didn’t seem too bothered!) and that lucky morning in early April, with frost on the ground, when I saw both ring ouzel and wheatear. The survey season seems to have passed by so quickly again but I won’t be too sad that summer is drawing to a close and autumn creeping nearer, like many of us I appreciate each season and the differences they bring. Roll on the blackberries!