Survivorship of Rehabilitated Juvenile Tawny Owls ( Strix Aluco ) released without Support Food,A Radio Tracking Study

Abstract

We investigated the survival of 57 rehabilitated juvenile Tawny Owls (Strix aluco) that were ‘hard released’ (without the provision of a release aviary or support food) by means of radio tracking. The birds were released in the month of August in three consecutive years: 2005, 2006 and 2007, in the counties of Somerset and Hampshire, United Kingdom. Tracking of the owls was successfully carried out for between three and 160 days. Mortality was recorded for 16 birds (28%). The transmitter was shed by 24 (42%) owls, the signal was lost for 12 (21%) and tracking was ceased for five (9%) owls. Survival of the owls was compared with results from previous studies on wild Tawny Owls and also rehabilitated ‘soft released’ Tawny Owls (released with provision of food and shelter after release) and found to be similar. This study suggests that employing costly and time-consuming soft release techniques may be unnecessary for juvenile Tawny Owls as their survival is not significantly reduced using hard-release methods. Measuring post-release success of rehabilitated birds of prey is discussed in relation to benchmarks used in previous studies.

Keywords

rehabilitation hard release soft release Tawny Owls Strix aluco survival juvenile radio track

Get full access to this article

View all access options for this article.

References

Aldridge

and Brigham

R.M.

(1988) Load carrying and manoeuvrability in an insectivorous bat: a test of the 5% ‘rule’ of telemetry. J. Mammal., 69, 379–382.

Bennett

J.A.

and Routh

A.D.

(2000) Post-release survival of hand-reared tawny owls (Strix aluco). Anim. Welf., 9, 317–321.

Coles

C.F.

and Petty

S.J.

(1997) Dispersal behaviour and survival of juvenile Tawny Owls (Strix aluco) during the low point in a vole cycle. In: Duncan

J.R.

, Johnson

D.H.

and Nicholls

T.H.

(eds.), Biology and conservation of owls of the Northern Hemisphere, pp. 111–118. USDA Forest Service, General Technical Report NC-190.

Csermely

(2000a) Behaviour of hand-reared orphaned long-eared owls and tawny owls after release in the wild. Ital. J. Zool., 67, 57–62.

Csermely

(2000b) Rehabilitation of birds of prey and their survival after release. A review. In: Lumeij

J.T.

, Remple

, Redig

P.T.

, Lierz

and Cooper

J.E.

(eds.), Raptor biomedicine III, including bibliography of diseases of birds of prey, pp. 303–311. Zoological Education Network, Lake Worth, Florida.

Dickens

M.J.

, Delehanty

D.J.

, Reed

J.M.

and Romero

L.M.

(2009) What happens to translocated game birds that ‘disappear’? Anim. Cons., 12, 418–425.

Duke

G.E.

, Redig

P.T.

and Jones

(1981) Recoveries and resightings of released rehabilitated raptors. J. Raptor Res., 15, 97–104.

Kaplan

E.L.

and Meier

(1958) Nonparametric estimation from incomplete observations. J. Am. Stat. Ass., 53, 457–481.

Kenward

R.E.

(2001) A manual for wildlife radio tagging. Academic Press, London, UK.

10.

Leighton

, Chilvers

, Charles

and Kelly

(2008) Postrelease survival of hand-reared tawny owls (Strix aluco) based on radio-tracking and leg-band return data. Anim. Welf., 17, 207–214.

11.

Martell

M.S.

, Redig

P.T.

, Nibe

and Buhl

(1991) Survival and movements of released rehabilitated Bald Eagles. J. Raptor Res., 25, 72–76.

12.

Martell

M.S.

, Goggin

and Redig

P.T.

(2000) Assessing rehabilitation success of raptors through band returns. In: Lumeij

J.T.

, Remple

, Redig

P.T.

, Lierz

and Cooper

J.E.

(eds.), Raptor biomedicine III, including bibliography of diseases of birds of prey, pp. 327–334. Zoological Education Network, Lake Worth, Florida.

13.

Molony

, Dowding

C.V.

, Baker

P.J.

, Cuthill

I.C.

and Harris

(2006) The effect of translocation and temporary captivity on wildlife rehabilitation success: An experimental study using European hedgehogs (Erinaceus europaeus). Biol. Cons., 130, 530–537.

14.

Newton

(1979) Population ecology of raptors. T & AD Poyser, Berkhamsted, UK.

15.

Overskaug

, Bolstad

J.P.

, Sunde

and Oien

I.J.

(1999) Fledgling behavior and survival in northern tawny owls. Condor, 101, 169–174.

16.

Petty

S.J.

and Thirgood

S.J.

(1989) A radio tracking study of post-fledging mortality and movements of tawny owls in Argyll. Ring. Migr., 10, 75–82.

17.

Snow

D.W.

and Perrins

C.M.

(1998) The birds of the Western Palearctic, concise edition, Vol.1, Non-Passerines. Oxford University Press, Oxford, UK.

18.

Southern

H.N.

, Vaughan

and Muir

R.C.

(1954) The behaviour of young Tawny Owls after fledging. Bird Study, 1, 101–110.

19.

Southern

H.N.

(1970) The natural control of a population of Tawny Owls (Strix aluco). J. Zool., 162, 197–285.

20.

Sunde

(2005) Predators control post-fledging mortality in tawny owls, Strix aluco. Oikos, 110, 461–472.

21.

Teixeira

C.P.

, Schetini de Azevedo

, Mendl

, Cipreste

C.F.

and Young

R.J.

(2007) Revisiting translocation and reintroduction programmes: the importance of considering stress. Anim. Behav., 73, 1–13.