Hawfinch survey update: Dec 2015 – Feb 2016

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By Marcus Ward, 25 April 2016

The winter period can be quite a busy time for the Hawfinch survey as I continue to monitor the core roosts and actively search out new roosts. For me this is the most exciting, rewarding, and at the same time frustrating part of the survey. It can often take many visits over a period of months (sometimes years) to pin down a new roost with many dead-ends thrown in along the way. There is nothing like the buzz of discovering a new roost, after months of fieldwork progressively homing in on the site. Often, the first hint that I am getting close is when I find the pre- or post-roost gathering site; however, this can often be hundreds of meters from the main roost itself, but it does provide the much-needed confirmation that I am searching in the right general area.

This winter I have been fortunate enough to pin down three new roosts, one of which I have been working on for two years, bringing our total known roosts to 22. With each new roost found we add to our knowledge of distribution of Hawfinch in the New Forest, and get a better understanding of numbers of birds using each area. Once a new roost is located it can often take a number of additional visits to get to grips with the dynamics of the roost, and establish the best vantage point for on-going monitoring of numbers of birds.

 

Adult male Hawfinch, in a classic pose in the treetops. Hawfinch will often head for the canopy at the slightest hint of potential danger; despite spending much time feeding on the ground, they are seldom seen on the forest floor
Adult male Hawfinch, in a classic pose in the treetops. Hawfinch will often head for the canopy at the slightest hint of potential danger; despite spending much time feeding on the ground, they are seldom seen on the forest floor

 

 

In general this winter, numbers of Hawfinch in the New Forest have been markedly lower than recent years – after a peak in November, numbers in most roosts dropped to a level around 25-30% lower than previous years, with one or two roosts ceasing to be used at all.

The main reason for this drop in numbers appears to be the poor beech mast crop in autumn 2015. Hawfinches rely heavily on beech mast as their main food source throughout the winter months, and so with an almost total failure of the crop last year, competition for food will be greatly intensified. Other important food sources for Hawfinch include holly berry seeds, yew and hornbeam, but once the winter thrushes have moved through in October and November very few holly berries remain in the forest, and both yew and hornbeam are thinly spread putting extra pressure on Hawfinches to find sustenance. This situation has therefore likely forced Hawfinches to temporarily move away from the New Forest in search of food elsewhere.

 

Monthly maxima at the Blackwater Arboretum Hawfinch roost for the past four years; as shown in the graph, numbers peaked in November 2015 but quickly dropped thereafter
Monthly maxima at the Blackwater Arboretum Hawfinch roost for the past four years; as shown in the graph, numbers peaked in November 2015 but quickly dropped thereafter

 

 

During the winter period, Hawfinch gather in small feeding flocks that appear to roam across the forest. However, by following these winter flocks I have found that each flock regularly visits a small number of favoured feeding sites that they rotate around during the course of the day. The flocks can be quite vocal when loitering in the treetops, but will go silent as they drop to the forest floor to feed. Hawfinch are often at their wariest when on the ground: they have a large body mass for their size and likely feel exposed and vulnerable when on the forest floor, flushing almost vertically to adjacent treetops at the slightest hint of danger. This goes some way to explain why a species that spends a large amount of time feeding on the ground, particularly in the winter months is rarely encountered actually feeding on the forest floor. They almost always hear you coming before you are even aware of their presence.

As we move into spring, the dynamics of the roosts start to change as Hawfinches prepare for the breeding season ahead. This often involves a lot of hustle and bustle at the roosts as birds form their pair bonds. The next update will describe some of this activity, and will cover the spring period from March to May 2016.