“Characterizing Golden Eagle Aquila chrysaetos Territorial Boundaries”

WTE skull with GE talons Derek Spencer, University of Highlands and Islands, Scotland

Characterising golden eagle territorial boundaries

Aims Confirming range boundaries Understanding nature of boundary interactions

Study Area Foinaven Special Protection Area (1000 km²), NW UK Classified for six golden eagle ranges Am studying 14 ranges Rugged, mountainous terrain Main prey- ptarmigan, grouse, voles, deer and sheep carrion, and assortment of other food

SPAs for golden eagles in the UK =>

->

Foinaven SPA and surrounding ranges

PAT: Predicting Aquila Territories

These are PAT modelled territories

Sources: McGrady et al 2002; McLeod et al 2002a,b; Fielding et al 2003; Fielding pers comm

Summary of the PAT model Golden eagle ranges can be approximated by Thiessen polygons with a 6 km cut-off.

Golden eagles are more likely to use habitat close to the range centre and close to a ridge.

They are unlikely to use some habitats (water, closed canopy woodland, arable, improved grassland, urban etc.).

These features were combined to produce an ‘expected use’ for each 50 m pixel within an eagle’s range.

More comprehensive descriptions of the PAT model can be found in McLeod et al. (2002) and Fielding et al. (2003).

Source: Haworth & Fielding, 2013

Field methods 2011-13 in the field Total of 275 days watching for golden eagles Focusing on boundary flights, displays, interactions Also studying range occupation, nesting success Line transects to assess food supplies Satellite tagging of young birds Historical investigations of ranges and land use

Territorial displays recorded (in order of frequency): Soaring – circling, spiralling upwards Patrolling – alone, along ‘boundaries’, and gliding Undulating – roller coasting, tumbling Talon tipping and grappling Arrow flights (chases) Eyrie drive past and looping (not just pair-bond reinforcement) – not as aggressive as above

Photo: Jeff Watson

Spent 275 days in the field over three breeding seasons Recorded all golden eagle flights (seen on 200 observation days) Recorded territorial boundary flights on 45 days, hence one every 6 days So, need to spend 48 hours in a given range to record just one territorial boundary flight! (Based on 8 hour observation day) Many field workers miss a lot of the activity I am about to show you!

Display flights across seven study golden eagle ranges

B

B N

N

B B

N

N

B N

No eagles’ land…

N

N

B

N N B

N

B N

Territorial boundary a long ridge!

Key findings‌ PAT model correctly identifies territorial boundaries Huge variation in activity between territories – why?

Most activity around boundaries of non-breeding pairs’ territories Neighbouring territories with breeding pairs have relatively little territorial activity So, most territorial activity centres on establishing a basis for occupation and nesting

Thanks to Martin Price, Liz Masden, Des Thompson Huge cooperation from estates

Thank you for listening

Nests

Some nests are surprisingly exposed

Distribution

Population Model Outline • Growth rate = Gains – Losses – Gains = Immigration + Births – Losses = Emigration + Mortality

• Immigration & Emigration are negligible • Births (fledged) – sporadic detail but relatively well known • Mortality – poorly known • FCS = 40% sub-adults survival, approx 95% annual for adults

Productivity • Spatial and temporal patterns • Explanations – – – –

Eggs? Fledged? 1 or 2? Offspring condition Prey availability Parental condition Weather

• Possible managment actions – Landscape management (large scale) – Prey enhancement (local) – Intensive intervention (Irish example)

Changes in productivity • Function of two processes that may operate in tandem or independently.

• Increases when more pairs are successful • Either more pairs laying and/or more pairs converting eggs into fledged young.

• Increase also possible when the number of successful pairs is constant but the number raising twins increases.

Prey

Understanding diet

Some Detail

Compare 05 & 06, 2006 few pairs laying but larger FR Table 3.3. Mean productivity data for the Uists 2005-2008.

Year 2005 2006 2007 2008 All

Occupied and known outcome Laid Chicks 27 21 8 24 13 8 25 21 15 24 21 17 100 76 48

Fledged Number young fledged 5 7 7 7 10 11 11 11 33 36

% laid 77.8 54.2 84.0 87.5 76.0

% % chick fledge (chicks (fledge /laid) /laid) 38.1 23.8 61.5 53.8 71.4 47.6 81.0 52.4 63.2 43.4

%chicks fledged 62.5 87.5 66.7 64.7 68.8

FR 0.26 0.29 0.44 0.46 0.36

Year 2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987

1986

1985

1984

1983

1982

Fledged per pair

Productivity (Mull, Skye, Argyll, Lochaber ~ 25% of all pairs)

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

May Rainfall Seems Important

Factors affecting survival • How long does an eagle live?

– Sub adult – Adult

• What determines survival?

– Disease (related to condition, prey types...)

– Starvation (combined with weather) – Accidents (broken bones in hunting accidents) – Intra and interspecific conflicts (WTE...)

– External (persecution, windfarms, other...)

• Management actions

Hare density

Grouse density

Red deer density

Sheep density

Changes in sheep density

Competition with WTE?

WTE skull with GE talons

Illustration: Keith Brockie

New studies, regions, habitats and issues…since 1997 • Hundreds of new references…phenomenally well studied • Scotland in nine regions…world regions • >250/440 ranges visited • Variation in nature and land use of Scotland • Constraints and opportunities…real conservation

WTE skull with GE talons Conflicts over predators‌

Highlands crofters blame sea eagles for leap in lamb deaths Sheep farmers say reintroduction of predatory birds to Scotland threatens their livelihoods

Claws out on a silent moorland A heated battle rages over the birds of prey threatening to destroy Britain's grouse

Photo: Ewan Weston

From Whitfield et al. 2004

Changes in sheep density

V

Range use and movements‌

Alma…in her first year…

Climate change‌

Haworth et al. 2009

Photo: Laurie Campbell

Photo: Jeff Watson