Migration Map

Migration Maps, Tõnn, Greater Spotted Eagle and Black Storks
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Riitta
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Re: Migration Map

Post by Riitta »

Thanks for the link, Kukelke. :D
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Kukelke
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Post by Kukelke »

September 30

Both yesterday and today a new batch of data came in (updated till the 29th). Osprey Tiiu hasn't moved much since the 27th but she moved about 5 km to the south since then, and seems to fly from tree to tree. No lakes or water at all are visible on the map, but perhaps that is because the satellite pictures of google were made in the dry period, and that there is a shallow lake there now, in the wet period.
Soon the dry period starts (end of October/start of November) and then the temporary lakes and watercourses will often dry out, meaning that Tiiu will have to move - that is, if my assumption that Tiiu is at such a temporary lake/river is right (if not, then I don't have an explanation of why she stays in an area without obvious fishing conditions).

Here some screenshots of the map, showing Tiiu's small movements, starting where the last update ended, at the 27th:

September 27 (from last update, see here: viewtopic.php?p=346572#p346572):
Image


September 27 (continued) - small movement of about 5 km to the south (first S-SE, then S-SW):
Image


September 28 - Tiiu explores the area a bit:
Image


September 29 - Tiiu moved some 60 meter:
Image
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Janne+Ais
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Post by Janne+Ais »

For me there seems to be a river and a small lake in the biggest extension of the "satellite view". Just near the "hook", which she flew lately. North and nearly the same way south again. Cannot explain it better and cannot show the picture.
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Kukelke
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Post by Kukelke »

October 3

Both yesterday and today new data came in, and osprey Tiiu seems to like the area as she is only making shorts trips. I think that my earlier assumption that the pictures of the satellite version of the map are made in the dry season, could be right, because Tiiu's movements on the map indicate that she is fishing at places which are shown as dry on the satellite version of the map. When you zoom in a bit more, you can see that there are still small ponds and parts of river arms visible on the map, scattered all over the landscape; probably the deeper parts of rivers, streams and marshes which don't dry out completely during the dry season. But the wet season isn't over yet, so it's highly likely that all these small ponds etc are still connected and larger than as shown on the satellite images.

Here the day by day pictures of Tiiu's movements in the area:

September 29 - Tiiu was perched in a tree at the lower left corner of the pic, and then flew some 500 m towards to N-E. Her movements indicate that she caught a fish here and ate it nearby:
Image

After that, the same day, Tiiu then flew about 17 km to the N-W and roosted there (note that there is a river about 7 km west of her roosting spot. Probably this river, which is called the Komoé River, won't dry out during the dry season, so we might see her frequent this area later in winter):
Image


September 30 - Tiiu woke up and flew west, to the Komoé River to get a fresh meal. It looks like she ate her breakfish in a tree on the banks of the river, before she moved back 7 km to the same area where she had been roosting:
Image

A closer look at the Komoé River where she fished. The parts with bare rock indicate that water is flowing there during the wet season and prevents vegetation to grow:
Image


Continued in next post
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Kukelke
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Post by Kukelke »

Contined from previous post

October 1 - Tiiu decided to move back to the area west of the town of Agnibilékrou, some 17 km S-E of her roosting spot, where she had been hanging out before she made this trip to the Komoé River:
Image

Close up from the same day, which indicates that she has been fishing here, in a now flooded area 1,5 km north of her previous roosting spot a few days earlier:
Image


October 2 - Tiiu flew crisscross over the probably still flooded area, most likely caught a fish, and perched in a tree there, some 50 m from where she has been roosting before:
Image

Close up:
Image
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Kukelke
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Post by Kukelke »

October 4

New data again, and osprey Tiiu hasn't done anything unexpected. On October 2, after the data was sent, she flew crisscross over the same small area as where she's now, and as usual her sharp turns over places which I suspect are shallow lakes in the wet season, indicate that she caught fish there, and ate it at some perch. She then roosted for the night next to a tree she used before to roost in.
In the early hours of October 3, just before the latest data was sent, Tiiu then flew 10 meter to the very same tree as mentioned above, the one where she has already been roosting previously, just at another branch (isn't it fantastic to be able to see such details thanks to advanced technology?):

October 2 - overview:
Image

October 2 - zoomed in on roosting spot:
Image

October 3 - Tiiu's jump to the tree next door:
Image
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Kukelke
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Post by Kukelke »

October 5

After osprey Tiiu jumped from one tree to the tree next door in the early hours of october 3 (see my previous post), and the data was sent, she decided it was time to visit the Komoé River again, some 25 km to the NW.
Tiiu must know the area well, because she visited exactly the same bend in the river, fished there, and then flew some 7 km east with her catch to eat it and roost in exactly the same tree she used on her previous trip to the Komoé River, the early morning of September 29.
In the morning of October 4, Tiiu flew off again, caught probably a fish some 250 m from her roosting spot, and then flew back to the SE again, to the same area as where she came from.

October 3 - Tiiu's trip to the Komoé River and roost 7 km east of the river:
Image

Same day, zoomed in a bit. Green circle where she caught fish in the river:
Image

Still same day, zoomed in on the tree she roosted in, and which she also used in the morning of September 29:
Image


October 4 - In the morning Tiiu flew back to the southeast again:
Image
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Kukelke
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Post by Kukelke »

October 7

After osprey Tiiu flew back to the southeast (see previous post) early on October 4, she only flew some 250m to the southwest, to the trees where she has been roosting before, and spent the night there:
Image


On October 5 Tiiu then flew 250m back to the northeast again, and her sharp turn on the map may indicate that she caught breakfish there, after which she flew some 700m almost straight north, to a tree. Probably to eat her meal. She then decided to fly 17km to the northwest again, to the same area 7km east of the Komoé River where she has been roosting and fishing before:
Image


Same day, zoomed in; Tiiu roosting in a tree:
Image


October 6, Tiiu probably caught a breakfish (green circle) near her roosting spot (purple arrow), and then flew some 800m south to eat it in a tree there:
Image


It will be interesting to see what Tiiu will do and where she will spend her days the next couple of weeks, as the dry season is approaching. In a month or so the shallow lakes where she has been fishing until now, will dry out and indeed look as on the map. Will Tiiu then move closer to the Komoé River and make that her home, or will she leave this area altogether and perhaps move a bit further south, towards the coast where there are big, shallow lagoons to fish in?
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Bea
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Post by Bea »

I can imagine that she stays as long as possible there during drying out times, it is easier fishing in low-water-level-areas.
Nature does nothing in vain (Aristoteles)
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Kukelke
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Post by Kukelke »

October 8

After osprey Tiiu caught a fish early on October 6 and ate it in a tree (see my previous post), the data for that day was sent. Later that day she flew again 17km back to the area in the SE, some 5km west of the town of Agnebilékrou where she uses to spend a lot of time.

On October 7 her movements indicate (= a sharp turn over an area without trees) that she caught a fish here, after which she flew 1km north to eat it there, perched in a tree. Tiiu then flew about 1 km south again and roosted there for the night.

Early this morning, on October 8, Tiiu's last position before the data was sent, indicates that she was foraging some 120m southwest of her roosting place last night. I bet that when I write this, she is already eating her breakfish somewhere.


Tiiu alternates now often between the area in the southeast, and that near the Komoé River some 25 km to the northwest; she spends 1-2 days in the SE, then 1 day in the NW. I wonder what's the reason behind this. As Bea pointed out yesterday, it's easier to catch a meal in ponds which are drying out (fish often gets trapped in such ponds), and these ponds are mainly in the SE of her wintering grounds. So why leave this abundance of food every other day?
There could be a couple of reasons for this behaviour, I think; the first is that fish isn't as abundant as I thought it was and that she therefore needs to forage elsewhere. The second reason could be what is decribed here (click link) by Paul Wildlifewriter: "the usual foraging strategy for an osprey (...) to not repeatedly exploit a single food source". And the third reason could be that she sort of inspects her main territory near the Komoé River every now and then, in order to keep other food competitors (first time migrating juvenile ospreys without a wintering territory yet, for example) away there, so that she's ready to move in there as soon as the dry season kicks in for real and these temporary ponds in the SE of her area are gone. Or perhaps a combination of these reasons.
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Kukelke
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Post by Kukelke »

October 10

A new batch of data again, so lets see what osprey Tiiu has done lately. As I wrote in my previous post, Tiiu was in the southeastern part of her wintering grounds again and most likely foraging early on October 8, just before the data were sent. The newest data seem to confirm this (a few sharp turns over treeless areas where I expect to be water now). After that she flew some 500m north again, towards these small ponds which are visible on the map.

Tiiu's roosting spot, a single tree with a good view over the surroundings, early on October 8:
Image

Her movements during the rest of October 8:
Image


On October 9 Tiiu decided once more to inspect the conditions at the Komoé River and flew to the northwest again. She visited the bank of the river, but I am not sure if she caught anything there because the map indicates dense riparian forest on the spot where she made a sharp turn (green circle). Maybe the area right under the trees is flooded now, but I have no idea if she could fish there with branches and bushes everywhere, as the undergrowth at those places tends to be very dense:
Image

After that Tiiu flew some 7 km east again, as usual when she visits this part of her wintering grounds. There she roosted in the same tree as she has used already a couple of times before:
Image


This morning, October 10, when the data were sent, Tiiu was already on her way back again to the southeastern part of her range:
Image
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Janne+Ais
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Post by Janne+Ais »

How exactly does the transmitter indicate the position? Maybe she was in the river, but on the map it is a little bit incorrect?
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Kukelke
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Post by Kukelke »

As far as I understood the accuracy of the transmitter is +/- 5m, but when Tiiu crossed the Sahara and she was roosting on the desert floor, changes in course of less than 5m were recorded (we could see her walk around, so to say).

The transmitter uses GPS to determine the exact location. At any given time there are at least 4 satellites covering every position on the planet, thus allowing for trigonometric calculations. Currently there are 32 GPS-satellites in orbit around the planet, but they aren't the same. The oldest ones have an accuracy of +/- 10m, while the newest versions are as accurate as +/- 1m (hence my +/- 5m).

In theory an old and less accurate GPS-satellite could have picked up Tiiu's signal and plotted it a tad bit wrong on the map. But even if we assume that is the case, Tiiu's position near the river would then indicate that she fished max. 2m from the shore. So yes, she could have caught a fish. Therefore I said that I wasn't sure if she caught anything there, but it could be, indeed.
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Kukelke
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Post by Kukelke »

October 11

New data again, and this time it looks like osprey Tiiu is doing something potentially interesting: After she visited the Komoé River on Ocotober 9, she didn't fly all the way back to her area in the southeast on October 10 (which until now has been her usual routine after visiting the river), but instead she stopped some 5km to the N-NW of her usual SE grounds. Tiiu perched in a tree there, on the edge of what looks like an agricultural field. Later on October 10, she then flew some 9 km to the northwest again, and perched there for the night, about halfway her southeastern area and the Komoé River.

Tiiu on October 10. Green circle is her stop near the agricultural field during the day, and the bird icon is where she roosted for the night:
Image

Same day, zoomed in on her stop near the field (green circle):
Image

I couldn't detect any foraging behaviour at first (sharp turns over open spaces), but after I had a closer look at Tiiu's flight path early on October 10, it could indicate that she caught a fish close to her roosting spot (which is some 7 km east of the river), and then flew some 9 km to that spot near the agricultural field (arrow is roosting spot, green circles are perhaps fishing attempts):
Image



Early today, on October 11, Tiiu then flew back to the area with the agricultural field, before the data were sent. No typical fishing behaviour detected so far today:
Image

Zoomed in again (green circle is her stop yesterday):
Image


Now the questions are: What is Tiiu doing there close to this agricultural field, and why didn't she return to her usual area in the southeast? I don't think she suddenly became a vegetarian, so it must be something else.
Could it be that her usual area in the southeast is drying out already? Or is there a lot of disturbance from human activity or noisy monkies, or predators in that area?
Maybe the area with the agricultural field lies lower and is still covered with shallow water to fish in?
Or perhaps Tiiu just wanted a change from her daily routines?

Questions, questions... lets see what the data the next couple of days can tell us about this change.
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macdoum
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Post by macdoum »

Kukelke Thanks for so much detail about our osprey's everyday flyabouts. :thumbs: :wave:
Carmel a member of SHOW .. I hope you love birds too. Its economical. It saves going to heaven.
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Riitta
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Post by Riitta »

I think so, too!
Thanks a lot, Kukelke, :wave: for your great job. :faint:
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Kukelke
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Post by Kukelke »

October 12

The latest data reveals that yesterday, osprey Tiiu went to the northwest again, to the area some 7 km east of the Komoé River, after she perched (or caught a fish?) near this agricultural field I mentioned yesterday. Her movements 7 km east of the river could indicate that she caught fish there. Early today, before the data were transmitted, she was back again near the agricultural field further to the southeast. But the last couple of days she hasn't visited the area where she stayed the first time after her arrival in Ivory Coast, near the town of Agnibilékrou.

So there could be a new pattern here: Tiiu fishes in one area and roosts in the other, but I am not sure which is which. In the area some 7 km east of the river, she has roosted a few times before, but short, sharp changes of direction there could indicate that she caught fish. However, some 350 m northeast of the agricultural field (which is about 15 km SE of the area east of the river) there are a couple of small ponds visible on the map. These ponds could be the remains of what is a much larger lake in the wet season. When zooming in on this area, the map shows that Tiiu picked the largest trees there.

So the most likely scenario, I think (please correct me if I'm wrong), is that Tiiu forages in the area 7 km east of the river, then flies with her fish 15 km to the area near the agricultural field to eat it undisturbed. But it *could* be the other way around too.
Because the big problem here is that the map on which Tiiu's data is plotted, isn't in real time; we don't know how old the satellite images used for the map, are. All I know, by deduction, is that the map depicts the area in the dry season, and that the actual landscape could be very different now. Not only because of seasonal changes in water levels, but also because humans could have altered the landscape (for example, socalled slash-and-burn agriculture is used in these parts of tropical Africa).

Wouldn't it be great if next generation of satellite transmitters for birds also had a built-in camera so we could not only study the movements of our feathered friends, but also see how their wintering grounds really look like.

-------------

:wave: Riita and macdoum, it's fun to do, as I like to (try to) solve puzzles, and maybe it's also a tiny contribution to a bigger understanding of what actually happens at their wintering grounds, just like the observation topics for the nestcams might help professional researchers with data provided via socalled citizen-science.
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Kukelke
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Post by Kukelke »

October 13

Yesterday, October 12, I reported that osprey Tiiu visited the area close to the agricultural field again in the early hours that same day, just before the data were sent. Today the data for the rest of October 12 came in (no data for today, October 13, is plotted on the map yet), and these data from yesterday show that Tiiu continued to fly southeast to the area where she stayed right after her arrival in Ivory Coast. Even more, when zooming in there, her movements indicate that she caught fish there.

October 12 - overview with Tiiu's roosting spot in the evening:
Image

Same day, zoomed in a bit more - arrow is the agricultural field; green circle is Tiiu's visit there on the 10th; yellow circle Tiiu's visits on the 11th and 12th; blue circle where Tiiu probably caught a fish on the 12th:
Image

Still October 12, max zoomed in on the area where Tiiu probably caught a fish, when she came from the agricultural field some 4 km further to the northwest, and her continued path south to her roosting spot, some 500 m away (I accentuated the movements with yellow so it's clear which path she took). The two sharp turns suggest that Tiiu tried to catch fish there. (Also note that this is very close to an S-shaped pond to the west, which is probably bigger now):
Image


So, the new pattern which I thought was developing, seems already broken, and Tiiu seems to be back on her old tracks.
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Kukelke
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Post by Kukelke »

October 14

No new data on the migration map today, but Paul Wildlifewriter was so kind to provide me with a link which shows the cellphone masts near Tiiu's wintering site:

Image
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Kukelke
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Post by Kukelke »

October 15

No new data so far today, but yesterday there came some new data on osprey Tiiu's movements after I posted, so I'll have a look at that.

On October 12 Tiiu flew to the southern edge of her range, as shown in my previous post. Later that day she flew about 500 m to the north, and roosted in a tree next to a small pond on the map. This pond is probably much larger now and connected to the other small ponds we can see on the map, and this solitary tree would be in the middle of the water. Ideal for an osprey to roost in, with other words:

Image


In the morning of October 13 Tiiu left her roost in the solitary tree (arrow), and her movements indicate that she went fishing right at her doorstep:

Image


That's all data we have so far. When the next batch of data arrives, we'll be able to see what she did later on October 13, and the next days.
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