This may help you with some ideas.

Cheers!

Baral et al. 2013. Population viability analysis of Critically Endangered white-rumped vultures Gyps bengalensis. Endangered Species Research 21: 65-76.

In order to get density the first thing you should consider is a survey method which allows you to account for detectability of the animals. Distance sampling is probably your best bet here. You can find many references about distance sampling here http://www.ruwpa.st-and.ac.uk/distancesamplingreferences/

You should be careful about designing your study, and field methods should be optimized to avoid assumption violation. This book might be useful in said case: Buckland, S. T.; Anderson, D. R.; Burnham, K. P.; Laake, J. L.; Borchers, D. L. & Thomas, L. Introduction to distance sampling - Estimating abundance of biological populations Oxford University Press, 2001 (note that there's an 1993 edition, available through the web site above).

Maybe some of our works on vultures could help.

On Egyptian vulture detectability:

https://www.researchgate.net/publication/230793853_Spatially_explicit_estimation_of_occupancy_detection_probability_and_survey_effort_needed_to_inform_conservation_planning?ev=prf_pub

On Egyptian vulture regional population trends and main threats in NW Spain:

https://www.researchgate.net/publication/231802955_Status_of_the_Endangered_Egyptian_vulture_Neophron_percnopterus_in_the_Cantabrian_Mountains_Spain_and_assessment_of_threats?ev=prf_pub

Regards!

Article Spatially explicit estimation of occupancy, detection probab...

Article Status of the Endangered Egyptian vulture Neophron percnopte...

Hi. I've used adehabitat (R package) to study the movement patterns (https://www.researchgate.net/publication/229429162_PATRONES_DE_MOVIMIENTO_Y_USO_DEL_ESPACIO_EN_LA_DISPERSIN_JUVENIL_DEL_BUITRE_NEGRO_(Aegypius_monachus)) (sorry, in spanish!)

Article Patrones de movimiento y uso del espacio en la dispersión ju...

Distance-based sampling is a good choice, but I do worry about its widespread use at times. Fundamentally, the formulation of the detectability function depends of the ability of the observer to accurately estimate distance. For vultures, I suspect that the distances you're doing with of rather large (say, larger than it would be if you were surveying a warbler or sparrow); thus, error at higher distances may be quite inflated. At the very least, I would look into some more modern approaches to modeling density/abundance/occurrence while accounting for detectability, such as N-mixture modeling (see work of Chandler). There are nice Bayesian approaches too that would enable you to push through any zero-inflated data you might have (something I haven't seen adequately explored programs like DISTANCE. Also, check out the "unmarked" package in R, as this is becoming a catch-all for most of the survey tools out there.

Two specific attributes of vultures that make them specifically challenging to monitor and survey are their varying level of colony formation and their long distance movement distances.

Therefore it might be a good idea to focus on surveying nests and colonies as a proxy for population density. Seasonal movements and partial migration reduces the link between the counts and the breeding population size. People are usually combining few approaches:

• Nest survey- this doesn’t require any special equipment and typically sets a good starting point. This is most beneficial during the breeding season when nest attendance is probably at it max. this can involve citizen science type of info, and can be a used to identify temporal trends in the population change. Obviously some colonies location change from year to year, but correcting for sampling effort etc this is quite reliable. Tree dwelling hooded vul are likely to be suitable candidates.

• Road survey- this is already discussed in previous answers. With vultures being attracted to road kill, I personally think that distance sampling is highly biased here, and a good quantification of the function is hard.

• Counts at naturally/ provided carcasses- this is good to estimate both species richness and relative densities, but up scaling to estimate population densities is problematic unless combined with re-sighting of marked individuals.

• Wing tags – this is done by catching adults with bait traps of by marking fledglings on the nest. This id labor intensive, but the equipment is not too expensive. The benefits are individual identification and sighting by random observes that add a lot to the data collection. Data analysis can be done with mark re sight approach and there is a massive literature and r packages for that.

• RFID tags- if massive captures are feasible (e.g. griffon vul in Israel, France and Spain), these tags are relatively cheap and provide presence absence data on remotely unobserved marked birds.

• GPS transmitters- this is obviously the best method for tracking vultures long range movements, but the high costs involved limit the sample size and applicability. Ideally, even a few gps tagged bird can assist in mapping colonies for the above listed methods.

Specifically for Africa there is an active list server whith many informative folks that can help you get started (https://groups.yahoo.com/neo/groups/africanraptors/info). Good luck!

Orr

Hi Japheth,

Check out the UK based Hawk Conservancy who are involved in African vulture research. http://www.hawk-conservancy.org/Research/Publications.shtml

While density estimates derived from soaring birds can be useful, I'd consider measuring nesting density as a first step and ideally use mark- recapture methods if you can fit wing tags to the birds. While this is a labor intensive method the data you get is high quality and marked birds can be observed at feeding stations and while soaring.

Good luck!

@Japheth Roberts: "...possible funding sources"

There are EU funds for this domain. Of course, concerning species that are of (prior) conservative interest (to the EU). In case You have some long-term intention (related to the vultures), please let me know - in order to get down to the eventual details.

Best regards!

I did similar work with Caracaras (see attached). They're ecologically very similar to vultures. Vultures can be so wide-ranging that truly knowing movement patterns would probably require a lot of aerial telemetry or satellite telemetry of marked birds. I know that's completely impractical in most cases, but maybe the EU funds mentioned above could be used?

@James Dwyer ”the EU funds mentioned above could be used”

Actually, we had several projects (focused on Species of Community Interest) with the support of the European Commission.

(some of them developed quite many years ago, as the one on which was based the article available at: https://www.researchgate.net/publication/258927945_POTENTIAL_MANAGEMENT_PLAN_FOR_CONSERVATION_OF_VIPERA_URSINII_FROM_THE_DANUBE_DELTA_BIOSPHERE_RESERVE_%28ROMANIA%29?ev=prf_pub )

Article POTENTIAL MANAGEMENT PLAN FOR CONSERVATION OF VIPERA URSINII...

Dear Japheth,

We have done similar works with Griffon vulture, Egyptian vulture and Bearded Vulture. Maybe you could have a look at http://paslopez.wordpress.com/publications/ and download several papers about the topics you are interested in (surveys, movement patterns and spatial ecology). Hope you find them interesting.

Regards,

Pascual

@J. Patrick Kelley "Distance-based sampling is a good choice, but I do worry about its widespread use at times.". I would actually say the exact same thing about N-mixture models. One should note that the assumptions required for distance sampling to work are well known and clear. On the other hand, I would say that the assumptions under N-mixture models are at best implicit in the model underneath, and hence not immediately clear for most practitioners, and the consequence of their failure mostly unknown. Therefore, I would be very careful before suggesting N-Mixture models over distance sampling on the basis of problems with their respective assumptions.

If you have time chek also https://www.researchgate.net/publication/232868252_Range_use_of_a_Eurasian_black_vulture_(Aegypius_monachus)_population_in_the_DadiaLefkimiSoufli_National_Park_and_the_adjacent_areas_Thrace_NE_Greece, https://www.researchgate.net/publication/255910492_Characterizing_Eurasian_black_vulture's_(Aegypius_monachus)_flight_movement_corridors_in_Thrace_a_need_for_conservation_on_a_landscape-level_scale?ev=prf_pub, https://www.researchgate.net/publication/247510205_Population_size_breeding_rates_and_conservation_status_of_Eurasian_black_vulture_in_the_Dadia_National_Park_Thrace_NE_Greece?ev=prf_pub

Article Range use of a Eurasian black vulture (Aegypius monachus) po...

Article Characterizing Eurasian black vulture's (Aegypius monachus) ...

Article Population size, breeding rates and conservation status of E...

I used a software called DENSITY to study the density of a very small population of mammals. It's an open source software. Could you try to use it! http://www.otago.ac.nz/density/ Might be usefull. Good luck!

Cristina

In addition to the answers you have received, you could try contacting the people I know are doing this in Arizona and southwestern United States. This is their web site: http://www.vulturemovements.org/hms/HMS_TV.htm

They have a long term study monitoring migration behavior since 2003.

Andres