January 30, 2016
I said in a post earlier this week that I’m interested in / trying to do is to measure conditions faced by individuals on the nonbreeding grounds on three different axes: prey availability, predator risk, and level of humans caused disturbance.
I thought today I could start by talking about how I’m looking at prey availability. There’s an obvious way to do it, of course. Collect the prey from the mudflats and count them. Easy peasy!
Ehhh. (Imagine that annoying game show buzzer)
I don’t do things the easy way! Ha. But seriously. Collecting mud samples and counting polychaete worms is fraught with problems and isn’t exactly easy. Many people have looked at similar things - even a current MS student in Chile trying to do it for two bays here on Chiloé (that’s literally his entire thesis) - and it’s a lot harder than it sounds and incredibly time consuming. I had thought about doing it here for every bay we go to (30+), but many concerns about time as well as that we don’t actually know what godwits prefer to eat so it’s still more or less a guess what the availability of the preferred species is, led my advisor and I to decide that we weren’t going down this path.
Instead, I’m using a couple different measures of foraging efficiency to approximate the relative food abundance. I do this using five minute long focal observations where I watch one individual for five minutes and follow and record what it does. For foraging efficiency, I’m most interested in three things - the number of times a minute an individual probes the ground, the number of successful probes where an individual swallows food, and the number of times an individual poops.
You can’t imagine how enthusiastically I say ‘pooped!’ into my recorder - they really don’t poop very often.
Using these measures, I can say a few things about prey availability. If they are probing and swallowing every time as fast as they can - prey is probably super abundant. When they probe don’t swallow, walk for three meters, probe again don’t swallow, prey probably is less abundant.
Today’s scan went very, very well. We went back to Chullec on Isla Quinchao. When we were here two weeks ago there was a big flock, but they flushed after half and hour and didn’t find any green flags. Today we had a big flock again (1,200) when we arrived. They stuck around for a full six hour scan. We found a new bird! A male that I banded this past summer (actually the last adult godwit I handled!). We were pretty happy to find him twice before and after low tide.
Then the sound of a jet plane overhead. A hundred godwits. The sound is really incredible and you can understand why these birds can fly 16,000 miles in a year and 6,000 miles without stopping.
Again! Another hundred. Two hundred coming in from the open bay. The flock was increasing quickly as they all began to roost. G finished a count (1,800), and we both said, “well geez there should be another green flag here”. Then G looked into his scope - “oh! I got a green flag!”
His magic touch struck again (I don’t think he even moved his scope at all) - a female we have seen twice at the next closest bay: Curaco. Then another green flag! A new bird! A male banded as a chick by Nathan and the second of the two that now breeds on plot (actually the female just mentioned is the other!). Then I spotted a new one - another male! We were up to 2,400 individuals on the flats!
Then whoosh (right during a focal observation) the jet engine took off and every, single, godwit took off into the air. There! A Peregrine Falcon ripped through the cloud of godwits, and they took off out over the bay and away.
We ended with three (three!) new individuals (it’s the end of January how did we get three!?!), and one other green flag for the day. We’re up to 24 - how big of a hump is it going to be to get to 25???
I said in a post earlier this week that I’m interested in / trying to do is to measure conditions faced by individuals on the nonbreeding grounds on three different axes: prey availability, predator risk, and level of humans caused disturbance.
I thought today I could start by talking about how I’m looking at prey availability. There’s an obvious way to do it, of course. Collect the prey from the mudflats and count them. Easy peasy!
Ehhh. (Imagine that annoying game show buzzer)
I don’t do things the easy way! Ha. But seriously. Collecting mud samples and counting polychaete worms is fraught with problems and isn’t exactly easy. Many people have looked at similar things - even a current MS student in Chile trying to do it for two bays here on Chiloé (that’s literally his entire thesis) - and it’s a lot harder than it sounds and incredibly time consuming. I had thought about doing it here for every bay we go to (30+), but many concerns about time as well as that we don’t actually know what godwits prefer to eat so it’s still more or less a guess what the availability of the preferred species is, led my advisor and I to decide that we weren’t going down this path.
Instead, I’m using a couple different measures of foraging efficiency to approximate the relative food abundance. I do this using five minute long focal observations where I watch one individual for five minutes and follow and record what it does. For foraging efficiency, I’m most interested in three things - the number of times a minute an individual probes the ground, the number of successful probes where an individual swallows food, and the number of times an individual poops.
You can’t imagine how enthusiastically I say ‘pooped!’ into my recorder - they really don’t poop very often.
Using these measures, I can say a few things about prey availability. If they are probing and swallowing every time as fast as they can - prey is probably super abundant. When they probe don’t swallow, walk for three meters, probe again don’t swallow, prey probably is less abundant.
Today’s scan went very, very well. We went back to Chullec on Isla Quinchao. When we were here two weeks ago there was a big flock, but they flushed after half and hour and didn’t find any green flags. Today we had a big flock again (1,200) when we arrived. They stuck around for a full six hour scan. We found a new bird! A male that I banded this past summer (actually the last adult godwit I handled!). We were pretty happy to find him twice before and after low tide.
Then the sound of a jet plane overhead. A hundred godwits. The sound is really incredible and you can understand why these birds can fly 16,000 miles in a year and 6,000 miles without stopping.
Again! Another hundred. Two hundred coming in from the open bay. The flock was increasing quickly as they all began to roost. G finished a count (1,800), and we both said, “well geez there should be another green flag here”. Then G looked into his scope - “oh! I got a green flag!”
His magic touch struck again (I don’t think he even moved his scope at all) - a female we have seen twice at the next closest bay: Curaco. Then another green flag! A new bird! A male banded as a chick by Nathan and the second of the two that now breeds on plot (actually the female just mentioned is the other!). Then I spotted a new one - another male! We were up to 2,400 individuals on the flats!
Then whoosh (right during a focal observation) the jet engine took off and every, single, godwit took off into the air. There! A Peregrine Falcon ripped through the cloud of godwits, and they took off out over the bay and away.
We ended with three (three!) new individuals (it’s the end of January how did we get three!?!), and one other green flag for the day. We’re up to 24 - how big of a hump is it going to be to get to 25???