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Wednesday, February 25, 2015

19-25 February 2015

In the last week 143580 has been moving around areas familiar to it. What is interesting is that during that whole week, it seems that the vulture never once visited the municipal rubbish dump at Al Amrat (where it was caught).  Currently it is moving between Al Hajar and Al Fayad, villages near the main Muscat-Quriyat road.  If you look back at earlier blog posts, you will see that this bird has used these areas before.  The assumption (at least my assumption) was that the Al Amerat rubbish dump played a huge role to the birds there, and that the birds visited daily.  This is apparently not the case, and implies that many more Egyptian vultures are using the area than we see at Al Amerat, and during the winter sometimes over 400 Egyptian vultures can be seen at the rubbish dump there!

Movements of 143580 during the week starting on 19 Feb 2015. (Click on the image and it will open in a new window, and be easily enlarged.)

Friday, February 20, 2015

Tutorial on the Technology

This blog post will be a short tutorial on the technology used to track the vultures.

The transmitters we use are "GPS PTTs" (Global Positioning System Platform Transmitter Terminals), and essentially they use two sets of satellites to locate the bird and to transmit data on its position and other information about the transmitter (battery status, activity of the bird, etc.) back to earth (us).  These two satellite processes are somewhat independent, but also integrated.  When working properly what happens is this:

The GPS receiver in the PTT calculates on a regular basis its location using the GPS system of satellites and stores that data on board the PTT.  Every two days the transmitter then turns on for a period of 10 hours and uploads that data via the Argos system of satellites, which then transmits the data to a ground station, which then forwards the data to us. The transmission of data via the Argos system also contains the other information about the tag or from sensors in the tag (when you hear the transmission it sounds like a fax).  The transmission signal sent by the PTT has not only those data, but has a stable signal pulse that is used by the Argos system to calculate an estimate of the PTT's position using geometry, the Doppler effect and information on the location, trajectory and speed of the satellites.

While this all sounds a bit complicated, the main tangible result is that for every bird we are tracking we get two sets of location data; GPS data and Argos data.  While the GPS data is typically more accurate, it takes more energy to incorporate the GPS technology, so for smaller birds Argos-only locations are possible.  This is not a problem for Egyptian vultures, and so we get both.

Below are examples of the Argos data and GPS data for the same bird over the same period of time, so that you can see the difference.  However, you can also see the similarities, which highlight that this bird has been making regular visits to the rubbish dump at Al Amerat and has recently be near Al Hajar.

GPS locations of 143580 during 30 January - 19 February 2015.
Argos locations of 143580 during 30 January -19 February 2015




Thursday, February 19, 2015

Sorry for the silence

I only realized today that we had not posted anything for a while.  Sorry.

Well, its a bit of good news and (apparent) bad news.  Here's the bad news.

143581 has gone missing.  It last transmitted on 4 February from a location just north of Ibra.  We waited some time hoping that we would get some transmission, but nothing yet.  The Environment Society of Oman sent one of their field biologists to investigate, but found nothing (which isn't entirely surprising),  So, we hope to mount a bigger effort in the near future to try to find out what happened.  Below is a map of the bird's movements between 30 January and 4 February.

Movement of 143581 during 30 January - 4 February 2015
The good news is that 143580 appears to be doing fine.  Since the end of January it has moved north and has been moving regularly between the Muscat municipal rubbish dump at Al Multaqa and the Al Amerat area of Muscat.  In Al Amerat it has been perching frequently on the high voltage powerline pylons.  In recent days it has been spending some time near Al Hajar in Wadi Aday.

Movement of 143580 during 30 January - 19 February 2015.

Monday, February 9, 2015

Early February 2015

The Egyptian vultures we are following via satellite continue to provide interesting information.  It's not that they are doing anything unusual, its just that we have so little information on this species in Oman, and so everything is new.  Below is what the birds have been doing for the last week or so.

143580 (red) wandered around early in the week, and has most recently returned to the rubbish dump where it was captured.  The behaviour of the birds since trapping has suggested that it was a negative experience for them, but with this bird returning to the site, it seems also that they recover from the disturbance in terms of avoiding the site.

143581 (blue) had been foraging south of Barka, but has since moved farther south, crossing the eastern Hajar Mountains, and is currently located near Ibra.

Movements of two Egyptian vultures during the first week of February 2015.

Monday, February 2, 2015

Egyptian vultures for beginners... and others

The Egyptian Vulture is a medium-sized avian scavenger with a wide Old World distribution that includes Arabia,  Egyptian vultures breeding in the northern parts of the range are migratory, moving into India, Arabia and Africa during the non-breeding season.  Birds from the southern part of the range seem to be resident nomads. The weight of evidence suggests that most immature Egyptian vultures spend the 4+ years prior to becoming breeders in Africa and Arabia. 
Adult Egyptian vulture flying over the Muscat municipal rubbish dump.
Egyptian vulture is regionally threatened in Arabia, and its global status is in decline, its historical distribution has been much reduced.  It has been classed as globally “Endangered” by Birdlife International (2015) since 2008. The mainland populations on the Arabian peninsula are thought to have declined by 90% in the last 50 years (Jennings 2010).   These declines are part of large (sometimes >95%) reductions in the population sizes of most Old World vulture species. 
Oman was thought to have a population of only about 100 pairs (Jennings 2010).  However, fieldwork (Angelov et al 2013), funded by the Environment Society of Oman, indicates that Masirah Island alone holds 65-80 breeding pairs of Egyptian vultures, a big increase on previously published information that about 12 pairs existed (Green 1949; Griffiths and Rogers 1975).  Recent surveys of scavenger use of rubbish dumps in northern Oman (Al Balushi et al 2013. Al Fazari and McGrady unpublished data, ESO unpublished data) support the idea that the Oman breeding population of vultures is likely bigger than earlier estimated, but also highlight the importance of Oman to pre-breeding (< 4 yrs of age) and migrating birds from elsewhere. Areas where numbers are not declining (perhaps like Oman) might be important “source areas” in any recovery that might occur, and safe areas for migrants are critical to species survival. 
In highlighting the importance of Oman, the numbers of vultures seen at rubbish dumps also highlights how little we know about them.  Where do they come from?  Where do they go to breed?  How long do they stay in Oman?  Do they move around Oman or the region?  How long do they live? What threats do they face in Arabia/Oman? All these questions are not only interesting, but important to conserving this species.

Globally, big conservation efforts are being applied to vultures (including Egyptian vultures), particularly in Eurasia and Africa.  This is due to huge declines in some of the most common species across their ranges.  Declines in many species are being driven by inadvertent poisoning by non-steroid anti-inflammatory drugs (NSAIDS).  Direct persecution, use of body parts for traditional medicine, electrocution, collisions and loss of habitat are all putting negative pressure on vulture populations worldwide.  The plight of Egyptian vultures has been the reason some support to our efforts and efforts like them has been given by the our partners (see logos to the right), the EU, the European Science Foundation, the Convention on Migratory Species (CMS), the Mohammed bin Zayed Species Conservation Fund, and a number of US zoos, just to name a few. 

Learn more about Egyptian vultures by downloading a brochure on them by using the links below, or the links to the right of this blog post:

Brochure on Egyptian vultures in English 

Quick update... 143580 is still south of Muscat, but wandering north from Hefaz.  143581 has been spending time south of Barka, roosting on the power lines there.  This bird has not visited the main Barka rubbish dump.  A couple of years ago we visited the Barka rubbish dump a number of times, but found no vultures there.  Indeed, the use of rubbish dumps around Oman by vultures is variable and the reasons for this are not immediately obvious (to us, at least).  Perhaps this research will help us better understand the reasons for this variation in use.