Tawny owl VHF telemetry studies in Northern Spain

Dr Iñigo Zuberogoitia X. Sólyomcsalogató (10. 'Falcon luring')

28th February – 1st March 2015 Szarvas, Hungary

Dr Iñigo Zuberogoitia & Gorka Burgos

• Knowledge about distribution and status: Six years censusing tawny owls in Bizkaia, Northern Spain.

• Zuberogoitia, I., Campos, L.F. 1998. Censusing owls in large areas: a comparison between methods. Ardeola, 45 (1): 47-53. • Zuberogoitia, I., Campos, L.F. 1997. Intensive census of nocturnal raptors in Biscay. Munibe. 1997, 49: 117-127. • Zuberogoitia, I., Martínez, J.A. & Alonso, R. 2011. Censusing owls. Some considerations to achieve better results. In

Zuberogoitia, I. & Martínez, J.E. (Eds). Ecology and Conservation of European Forest-Dwelling Raptors, pp 137-145. Diputación Foral de Bizkaia. Bilbao.

• Zuberogoitia, I. &. Martínez, J.A 2003. Cárabo Común. En R. Marti y J.C. del Moral. (Eds). Atlas de las aves reproductoras de España. Pp 320-321. Dirección General de la Conservación de la Naturaleza-Sociedad Española de Ornitología. Madrid.

• Zuberogoitia, I. 2012. Cárabo común. En SEO/BirdLife. Atlas de las aves en invierno en España 2007-2010, pp 336-337. Ministerio de Agricultura, Alimentación y Medio Ambiente-SEO/BirdLife. Madrid.

• Knowledge about vocal behaviour of tawny owls • Zuberogoitia, I. & Martínez, J.A. 2000. Methods for surveying Tawny Owl Strix aluco populations in large areas. Biota, Vol 1,

Nº 2: 137-146.

• Knowledge about breeding of tawny owls • Zuberogoitia, I., Martínez, J.A., Iraeta, A., Azkona, A. & Castillo, I. 2004. Posible first record of double brooding on Tawny

Owl Strix aluco. Ardeola, 51 (2): 435-437. • Zuberogoitia, I. 2011. Weather influence on breeding success of the tawny owl on the southwest limit of Eurosiberian

Region. In Zuberogoitia, I. & Martínez, J.E. (Eds). Ecology and Conservation of European Forest-Dwelling Raptors, pp 184-189.

• Knowledge about inter-guild relationships: • Zuberogoitia, I., Martínez, J.A., Zabala, J. & Martínez, J.E. 2005. Interspecific aggression and nest-site competition in a

European owl community. Journal of Raptor Research, 39(2): 156-159. • Zuberogoitia, I., Martínez, J.E., Zabala, J., Martínez, J.A., Azkona, A., Castillo, I. & Hidalgo, S. 2008. Social interactions

between two owl species sometimes associated with intraguild predation. Ardea 96 (1): 109-113.

Background

Background

• Other works related to the vocal behavior of owls: • Martínez, J.A., Zuberogoitia, I., Colás, J. & Macía, J. 2002. Use of recorder calls for detecting Long-eared Owls Asio otus.

Ardeola, 49 (1): 97-101 • Martínez, J.A. & Zuberogoitia, I. 2002. Factors affecting the vocal behaviour of Eagle Owl Bubo bubo: effects of sex and

territorial status. Ardeola, 49 (1): 1-10. • Martínez, J.A. & Zuberogoitia, I. 2003. Factors afecting the vocal behavior of Eagle Owls Bubo bubo: effects of season,

density and territory quality. Ardeola, 50 (2): 255-258. • Zuberogoitia, I., Zabala, J., Martínez, J.A., Hidalgo, S., Martínez, J.E., Azkona, A. & Castillo, I. 2007. Seasonal dynamics in

social behaviour and spacing patterns of the Little Owl Athene noctua. Ornis Fennica 84, 173-180. • Zuberogoitia, I., Zabala, J. & Martínez, J.E. 2011. Bias in little owl population estimates using playback techniques during

surveys. Animal Biodiversity and Conservation, 34.2: 395-400.

• Other works related to the habitat selection of owls: • Martínez, J.A., Serrano, D. & Zuberogoitia, I. 2003. Predictive models of habitat preferences for the Eurasian Eagle Owl Bubo

bubo: a multi-scale approach. – Ecography. 26: 21-28. • Martínez, J.A. & Zuberogoitia, I. 2004. Effects of habitat loss on perceived actual abundance of the Little Owl athene noctua.

Ardeola, 51 (1): 215-219. • Martínez, J.A. & Zuberogoitia, I. 2004. Habitat preferences and causes of population decline for Barn Owl (Tyto alba); a multi-

scale approach. Ardeola, 51 (2): 342-344. • Martínez, J.A. & Zuberogoitia, I. 2004. Habitat preferentes for Long-eared Owl Asio otus and Little Owl Athene noctua in semi-

arid environments at three spatial scales. Bird Study, 51: 163-169. • Zabala, J., Zuberogoitia, I., Martínez, J.A., Martínez, J.E., Azkona, A., Hidalgo, S. & Iraeta, A. 2006. Occupance and

abundance of Little Owl (Athene noctua) in an intensively managed forest area in Biscay. Ornis Fennica 83: 97-107. • Martínez, J.A., Zuberogoitia, I., Martínez, J.A., Zabala, J. & Calvo, J.E. 2007. Patterns of territory settlements by Eurasian

scops-owl (Otus scops) in altered semi-arid lanscape. J. Arid Environm. 69: 400-409.

Background Goals

The main goals we planned were: To study two different populations in two different types of forest structure: large deciduous forests with field-grass for cattle, mainly cows, and few buildings (Burceña) vs pine timber plantations with dense but disperse buildings with gardens and field-grass for sheep (Durango).

Background Goals

Burceña Burceña

Durango Durango

Background Goals

The main goals we planned were: Of course, we wanted to describe the habitat selection, considering both foraging and resting habitats. The main questions were: 1. Could we hope differences in density and home range? 2. Could we hope differences in habitat use? 3. Could we hope differences in breeding success? 4. Could we hope differences in vocal behavior?

Background Goals

The main goals we planned were: But also we wanted to know: 1. Is the vocal behaviour related to population density, habitat quality and individual

quality? 2. Do tawny owls use vocal behaviour in the borders of the home range? Or

perhaps it is also conditioned by the habitat and population structure? 3. And, once in this step, could we hope differences in the results of census using

broadcasts?

Background Goals

The main goals we planned were: And, trying to go further: 1. Do the habitat quality condition the moult of tawny owls? 2. Do the human density and the use of natural resources condition the behaviour

of tawny owls?

Background Goals Methods

Study area selection: 1- Radio-tracking tawny owls with no financial support (we received a little grant for materials – Gobierno Vasco and Gorka Burgos received a grant during three months from the Santander Bank) We bought 20 transmitters (Biotrack) for one year of life-span. We needed to trap 10 tawny owls in each study area. But, what is more important, we needed to trap neighbours. All birds in the same two areas. We selected these two areas because I live in one and Gorka Burgos (he is doing his PhD Thesis with this project) lives in the second. It is important to make it easy! We were to spend hundreds of hours during daytime and nights in the following years, so we needed to have easy and quick access to the areas.

Background Goals Methods

Trapping owls: 2- We started trapping four owls in March 2013 in one area and we waited till the autumn for continuing. We trapped tawny owls using a broadcast (voices of male, female or both) and a mist-net (21 x 3 m, 7 cm mesh). The best season to trap tawny owls was the period from November to January. For trapping tawny owls: 1- we playbacked the records and waited 10 minutes for answer. 2- If we obtained weak answer or silent, we did not set the net and moved to another point. 3- If tawny owls came hooting and flying above the tape, we set the net cutting the trajectory between the canopy. 4- We stopped the tape and then we set the net until 9 m height, and latter we switched on the tape again. 5- Normally the owl is trapped in few minutes if the net is correctly set.

Background Goals Methods

Tagging owls: 3- We ringed, measured, dated and took the moult card of the trapped owls, and finally we put the tags in the back of the owls. We sexed tawny owls listening them, before trapping!

Background Goals Methods

Monitoring radio-tracked owls: 4- We used homing technique in order to detect the positions of owls with precision. 5- To avoid pseudoreplication we only obtained one position per night, 2-4 nights per week and one-two diurnal positions per week. 6- We pointed out the position, data and time, the type of forest, the activity and the weather. But also we pointed out every time that the target owl produced a voice and the type of voice. We also pointed out the vocal activity of every tawny owl (target or no) detected during the radio-tracking period.

Background Goals Methods

Processing data: 7- We noted every position each following day in a GIS software (Quantum Gis) .

Background Goals Methods

Testing vocal activity – census validation: 8- We tested the response of target owls to the broadcast during winter. We tested the response 3-4 times/individual from November till February. We used different voices each time (tawny owls are able to recognize the voice of their neighbours and can learn about the voice you use to call them). Basically, we are trying to develop the same protocol that we used in:

Background Goals Methods

Monitoring breeding success: 9- We detected and described nesting sites and we monitored the breeding success of each monitored owl. 10- We set camera traps and infrared barriers with a camera in the nest sites in order to monitor the type of prey items that each owl carried to the nestlings.

Background Goals Methods

Analysing prey abundance: 11- We used sherman traps in order to analyse the abundance of micro-mammals in different type of forests and to compare it with the use rate of target owls in both areas.

Background Goals Methods

Testing moult pattern and habitat quality: 12- Since we only had 20 tawny owls, we trapped the neighbours in the both areas in order to obtain a moult card of each one. We wanted to reach a sample size enough for analysing these data.

Background Goals Methods First results

Id Age Sex Capture End N positions Zelai 4cy+ F 1 march 2013 30 July 2014 195 Julen 4cy+ M 1 march 2013 23 July 2014 210 Jaimito 3cy M 16 march 2013 30 July 2014 191 Agur 4cy+ F 22 march 2013 17 July 2014 207 Juanito 4cy+ M 18 september 2013 Active 217 Ixone 5cy+ F 12 October2013 24 December 2014 178 Ontza 1cy F 6 December 2013 11 Ferbruary 2014 31 Golfo 4cy+ M 6 December 2013 Active 154 Esmeralda 4cy+ F 29 December 2013 Active 129 Rober 5cy+ M 22 February 2014 Active 131

Id Age Sex Capture End N positions Aranzadi 4cy+ M 9 October 2013 Active 275 Irene 4cy+ F 25 October 2013 Active 236 Garai 4cy+ F 29 November 2013 Active 98 Gorrotxa 5cy+ M 1 December 2013 Active 205 Sarria 3cy+ F 1 December 2013 Active 203 Maruri 4cy M 7 December 2013 Active 197 Houdini 4cy+ M 11 December 2013 Active 194 Kiwi 3cy+ M 21 December 2013 Active 194 Nora 4cy+ F 28 December 2013 Active 195 Santi 3cy M 30 December 2013 Active 191

Results of tracked owls We are still tracking 14 tawny owls, thus these are preliminary results.

Burceña

Durango

Background Goals Methods First results

Burceña Durango

Population density Vocal activity Breeding succes Micro-mammal abundance

Lower Higher

Higher Lower Home range

Background Goals Methods First results

Burceña Durango

Holes in trees 3 3 Buildings 1 2 Number of birds that did not breed 8 4

Background Goals Methods First results

We still need to finish our field work and after the oncoming breeding season (there are two females incubating now) we will start to analyse data in order to test the hypothesis. I hope to publish our results in few years!