I am looking for a survey or census method that can be used to assess the national population of Eagle Owls in Romania. Does anybody know about publications containing methodology for this, or does anybody have some experience with Eagle Owl surveys?
You could search for information on the web for the Christmas Bird Count that they conduct in North American every year. Given that it works with volunteers, their methodology should be easily found (public).
Also, I recall that Owls can be effectively surveyed using reccorded Calls to be played and then taking note of response calls by animals. I don't have any litterature to suggest in particular as I never worked with birds, but see for example this link form "call-based" surveys done in British Columbia, Canada:
http://www.ilmb.gov.bc.ca/risc/pubs/tebiodiv/owl/owl_protocols_2k6.pdf
hope this helps.
Cheers!
Thanks Daniel, we have a similar Common Bird Census program in Romania too, but the method is not suitable for Eagle Owl. We use owl calls for Tawny Owl, Ural Owl, and Pigmy Owl surveys (and indeed, Eagle Owls also), and we usually find the birds if their there. I am more interested in questions like how many points should we use? when should we use the sound? where should we look for it among potentially good sites? The link is quite interesting though, it may provide partial answers :)
Dear Atilla,
I find it very interesting to carry out a census of Eagle owl in Romania, but I've worked with this species and I know how hard it can do a surveillance in a so huge area (aprox 240.000 km2). I think the first thing to ask yourself is know what are your aims (to know populations trends, distribution, breeding pairs...), because some of them are very difficult to achieve in the short term. For example if you can not cover the entire study area, could be more interesting carry out a trend population analysis during year by year.
As example in Spain it's performing the "Noctua" program. It is a monitoring study coordinated by SEO (BirdLife partner in Spain) since 1997. It's purpose is to assess owls population trends at national scale. This is conducted by volunteers with a well defined methodology in a 10 km squares UTM. If you are interested in the methodology, I attached the link, but unfortunately it's only available in Spanish.
http://www.seo.org/2012/04/13/noctua/
Results 2006-2011
http://www.seo.org/wp-content/uploads/2012/04/Resultados_noctua_11c.pdf
But if your aim It's to detect territories or breeding pairs, I suggest you should define suitable nesting areas to optimize the fieldwork. A good option to identify this areas are using owl sightings to generate a SMD species distribution models. For this, you can use some spatial modelling softwares such as MAXENT or ENFA that use only-presence data.
Regarding the census methodology in suitable areas, first, I think that can be very helpful for you the review of owl census methods by I. Zuberogoitia et al. published in: Ecology and Conservation of European Forest-Dwelling Raptors (see link below).
In this chapter they show the use of conespecific call could be an unsuitable method to census Eagle owl. In fact, currently almost all monitoring were performed by spontaneous calls. Morover, listen stations not always works well. In Southeastern Spain where was recorded one of the most high-density population for this specie to date, we cannot census the population by calling stations because we have difficults to make a breeding pair stimate due to so many males singing at the same time. In this case, it was more effective to look for nests and perches directly.
https://www.researchgate.net/publication/233083764_Distribution_and_breeding_performance_of_a_high-density_Eagle_Owl_Bubo_bubo_population_in_southeast_Spain
Finally, the distance between stations, I think it depends directly about the breeding density of the specie. In Noctua program, stations were distanced 1,5 km. This seem a good distance in a medium density population (populations with mean NND c.a. 2 km), but could be very close in sparse population, or for example in our case very far.
I hope it will be helpful
Best regards
Article Distribution and breeding performance of a high-density Eagl...
Chapter Censusing owls. Some considerations to achieve better results
Thank you Juan for the valuable answer!
As you may know, every country in the European Union has to report the population, trend and distribution in every 6 years. Romania is writing this report for the first time, and we have to write a census methodology for 270 species, one of them being the Eagle Owl. The problem is, we don't have a quit usable methodology that can yield us information about the national population size (this is the most important, because we can't say anything about trends since we don't have multi-year data). So far, on smaller scales, we surveyed suitable habitats by listening to calling males at dawn, but as you said, the territory is huge, and we have to find a good method to extrapolate from. I will dig in the literature you kindly gave, hope to find something in it:)
Wish you the best,
Attila
I agree that for optimize your work, you must select area. Or you can select some square network (10x10 km). When you aim is to know trend of national population then the square network could be one reason. Very useful can be bioacoustical monitoring (in Slovakia and Czech republic are used digital voice recorders). The digital voice recorders you can put on many localities (quarries, cliffs). You can record all nights or some part of the night.
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