Thursday, 11 February 2016

A Dipper at long last!

Since I lived in Wales I have ringed Dipper pulli in the spring but never made an attempt to catch adult birds until recently. My neighbour allows me to use his land where the river is far more accessible than at the bottom on my garden. After several failed attempts in the last couple of weeks I decided to  investigate further the potential of the river at home.

At the end of my garden the ground drops away to the river so the first thing was to find a ladder and position it safely so I could get down. Once down I cleared away the undergrowth and soon got a 4metre net spanning across the river. I don't know what other people do but my concern was having the bottom shelf too low and risking a bird flying into the bottom shelf and getting wet. The male is a bigger bird than the female and its weight range from the BTO Birdfacts is 62gms to 74gms so I got a a piece of a tree branch about 40mm in diameter and cut a length until it weighed 100gms. I then dropped this piece of wood into the bottom shelf of the net in different places along its length and adjusted the bottom shelf height so the wood was hanging about 3 inches from the water.

As I suspected the dipper I caught today was in the bottom shelf and was well clear of the water with a weight of 64.9gms

Using Svennson and again BTO Birdfacts the male bird plumage is the same as female plumage so the bird was unsexed because of this. However the male bird is larger than the female and the biometrics are as follows:

Male 62gms to 74gms
Female 52.5gms to 69gms.

The weight of my bird was 64.9gms and there is a clear cross over so still unable to sex the bird.

Wing length
Male 93.5mm to 101mm
Female 86mm to 92 mm

The wing length of my bird was 95mm so I concluded it was a male.

The age of the bird was a juvenile based on the white or greyish white tips of the PC's and GC's.

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