Hawfinch tracking in the New Forest – Phase 1

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By Andrew Colenutt, 8 September 2019

Preliminary summary of fieldwork 2019 – prepared by Andrew Colenutt

Hawfinch is an iconic species with very limited distribution within the UK, and have experienced a dramatic decline across the UK over the past decade with the bulk of the population now largely restricted to three core areas, mid-Wales, the Forest of Dean/Wye Valley and the New Forest. The New Forest has been highlighted as one of the last strongholds of the species in the UK.

Andrew radio tracking at dusk, Slufters South
Andrew radio tracking at dusk, Slufters South

Aim

In order to determine movements of Hawfinch within the New Forest and ascertain the range and favoured feeding sites of breeding Hawfinch, the project aimed to tag a total of 10 Hawfinch with dual high resolution GPS/radio tags, comprising a mixture of known regular visitors to the bait station and previously un-ringed individuals. This methodology enabled the team to identify and further understand which locations and habitats are important for breeding Hawfinch and in particular, how widely they range. All ringing activities and deployment of tags were undertaken under special licenses issued by BTO, Forestry England and RSPB.

Method

From extensive fieldwork undertaken by Marcus over many years using trail cameras, observing behaviour of individuals and identifying those that were regular return visitors to the bait station, suitable candidate Hawfinch were selected. The majority of the targeted Hawfinch were previously colour-ringed with comprehensive life histories, but a few unknown individuals were also captured, colour-ringed and tagged.

GPS/Radio tag weighing in at 1.05g
GPS/Radio tag weighing in at 1.05g

The project used a new generation of small dual GPS & radio tags weighing just 1.05g  (average New Forest Hawfinch weighs c60g) that are applied directly on the birds back, the tag is designed to fall off after 10-14 days. Each of the 10 Hawfinch had a tag programmed to an individual radio frequency so that individual birds can be identified as they are tracked. No more than three tags were deployed in the field at any one time so survey effort could be maximized and the team could focus on each live tag. The radio signal range of the tags varied between 4km and 50m, depending on weather conditions, woodland density and terrain. The RSPB kindly loaned a receiver unit and a pair of aerials, and HOS loaned a couple of aerials as spares.

And so it begins... first morning of Hawfinch tracking, Bolderwood, 26 April 2019
And so it begins… first morning of Hawfinch tracking, Bolderwood, 26 April 2019
Tracking with receiver and aerial, Bolderwood
Tracking with receiver and aerial, Bolderwood

 

A team of dedicated volunteers tracked the birds in the field both during the day to assess where the off-duty male forages for food and overnight to discover where the off-duty males roost and assess roost site fidelity. The tracking team recorded presence and absence of the targetted tagged Hawfinch, and weekly updates were circulated with details on individual Hawfinch locations, tracking histories etc. to ensure team were informed and maximise survey effort.

Examples of initial GPS data

Adult male Hawfinch IP

Adult male Hawfinch IP (taken in 2018 with DN colour-ring)
Adult male Hawfinch IP (taken in 2018 with DN colour-ring)

 

GPS data - radio tracking yet to be overlaid
IP’s GPS data – radio tracking yet to be overlaid
  • Roosted in ivy-clad Oak close to the nest in Bratley Inclosure
  • Multiple feeding trips to isolated Holly Holm at Fritham Cross
  • Relatively site faithful, staying close to nest site in Bratley Inclosure

Adult male Hawfinch BN

GPS data - radio tracking yet to be overlaid
BN’s GPS data – radio tracking yet to be overlaid
  • Bred in mixed mature Beech/Oak
  • Frequently foraged in various patches of Holly across the Bolderwood area
  • Roosed nightly in the established communal roost at Bolderwood Grounds
Tag retrieved 7 June beneath Beech, Pund Hill, near Bolderwood Grounds
Tag retrieved 7 June beneath Beech, Pund Hill, near Bolderwood Grounds

 

Adult male Hawfinch H3

Adult male Hawfinch H3
Adult male Hawfinch H3

 

H3's GPS data - radio tracking data yet to be overlaid
H3’s GPS data – radio tracking data yet to be overlaid
  • Bred in Oak along Highland Water, west of Puckpits
  • Frequently visited various Holly clumps but spent most time in locality of nest
  • Roosted over 1km to south-east in established communal roost

Summary of Results

During the 2019 field season 10 tags were deployed, with an 80% recovery rate. Of the eight tags retrieved, seven were located in the field using the radio tracker once they had fallen off the Hawfinch and one was retrieved from a bird recaught at the bait station. Of the two that were not retrieved a significant volume of data was retrieved from the radio tags over a period in excess of four week on each individual.

The tag dropped by IA is well camoflaged in the leaf litter
The tag dropped by IA is well camouflaged in the leaf litter

 

A significantly large and rich dataset was successfully gathered, with the high resolution GPS data being integrated with radio tracking records and visual observations. Initial Results include:

  • 33 Hawfinch caught and colour ringed
  • Over 600 re-sightings of colour ringed Hawfinch via trail camera
  • 10 dual GPS/radio tags deployed and active in the field between 26th April and 17th July
  • 8 tags retrieved enabling download of high resolution GPS data
  • A dozen volunteers successfully radio tracked all tagged birds daily gaining multiple position fixes throughout the day and at roost in the evenings
  • Tagged individuals ranged within 6km of the ringing station
  • Foraging areas for seven off-duty males mapped utilising a mix of habitats
  • Several new important feeding sites identified
  • Off-duty males recorded in both communal and isolated roosts in variety of tree species
  • Seven breeding attempts mapped, mainly in ivy-clad Oak and Beech
  • Seven new communal roosts identified (twelve communal roosts used in total)
  • Variable fidelity levels associated with roost sites
  • Minimum of two new creche site locations identified

Achieving an 80% retrieval rate of tag is impressive and the combination of GPS and radio tracking data that the team have compiled is invaluable and will inform conservation and management of many important sites and habitats, and has furthered our understanding of this iconic species.

Marcus writing up tracking results from a long evening tracking resulting in identifying a previously unknown Hawfinch roost site
Marcus writing up tracking results from a long evening tracking resulting in identifying a previously unknown Hawfinch roost site

 

The project will move into the data analysis phase but field work will continue. Delving into the data has already highlighted some intriguing movements and locations where these birds visited for variable lengths of time, so there will be sites and habitats that will need assessing, and new and existing roosts to monitor. We are also preparing for a funding bid for phase 2 of the project.

Acknowledgements

Marcus and I would sincerely like to acknowledge the following team members for dedicated tracking and support: – Helen Schneider, David Brookes, Kevin Sayer, Carmen Green, Ellie Mayhew, Marc Baldwin, Paul Henegen, Richard Reeves, Tara Dempsey, Barry Page, Jamie Ward, Jessica Ward, Zoe Ward, plus various Forestry England keepers.

Thanks also to Andy Page and Russ Wynn for support and advice, Marc Moody, and to the RSPB and HOS for loan of receiver and aerials and The Barker Mill Foundation, Hampshire Ornithological Society and Ted Barnes for kindly sponsoring the project.