Risk and Benefits of Early Migration
Here on my nature blog here you will constantly see me noting my first of the year sightings! Normally those are the birds trying to be the first on their breeding grounds. These early birds are the experienced adults taking advantage of the many benefits of arriving early. Those males who arrive first will have their first choice in the most suitable nesting habitat and provide a better chance for the males to be pair up with a female. These earlier nesting pairs will then have a longer nesting period with a better fledgling success rate. Those individuals that show up later will then result in a less suitable habitat where they could have less available food for their young. Obviously this will reduce their chances of producing successful fledglings and open up the opportunity for predators finding their nest.
These long-distance migrants have many hazardous obstacles that the birds will need to avoid during their migration. My Ornithology text book by Frank Gill states “More than half the small land birds of the Northern Hemisphere never return from their southbound migration”. This is so hard to believe but there are so many physical risk that they encounter like: exhaustion, predators or even the weather. It was my post yesterdays where I discussed temperatures being in the ~70sF (Tuesday’s 1/2 day off). There were a few species including a dragonfly which I had listed as my first for the year find. Could they be risking their lives for the possible benefits of arriving early?
I said in that same post yesterday “I noticed that the Eastern Bluebirds and Tree Swallows had already started fighting over some of the bluebird boxes”. This comment was stating that local Tree Swallows have finally arrived and they should start nesting soon. I have been seeing these Tree Swallows since last Saturday and their main food supply includes flying insects which they catch while in flight. Last evening the temperatures got low enough that we had mixed freezing rain and snow. No doubt temperatures will reduce the numbers of flying insects and limit the opportunities for Tree Swallows to obtain food. I am currently looking outside with 2-3 inches of snow on the ground and there is no weather changes predicted until after Easter Sunday (it will be in the 40’s then). Doing some reading on Tree Swallows and when the weather is bad they have been known to feed on berries. But will these berries be enough food to survive a snowstorm? After work I had observed hundreds of Tree Swallows flying adamantly searching for food along the Red House Lake (lucky the lake is warm enough to provide a few insects and not need to rely entirely on berries).
Last evening as we were getting the freezing rain and snow I happened to passed a few of the nest boxes with numerous Tree Swallows sitting on top of them. I continued watching the swallows through my binoculars and there were 3, 4 and then 5 swallows entering one of the boxes in a matter of seconds. I jumped out of the truck and tried to approach the box for a photo for the blog! This one bird didn’t seem at the least bit concerned that I was there (see photo above). Eventually it flew away and I then peered into the box with this cute little swallow peaking out at me. How many were inside the box is hard to guess but there was no way that I would disturb them any more than I had already. These birds were apparently stressed and I probably shouldn’t have disrupted them like I had already.
But, where does a field biologist draw the lines in protecting the birds vs. letting nature take its course? From past experience I know those birds on the bottom of the bird packed box will end up suffocating! No matter what I do there will always be the birds on the bottom that will end up dieing! Will those on the bottom give a needed advantage to other individuals on top to survive this 5 day winter storm? Is arriving early too much of a risk or will those that survive greatly benefit from being the first on site? Or will the early Tree Swallows be too weak to protect the prime nest boxes and the stronger later migrants get the best pickings? So many questions and I do apologize for my rambling. This is all I could think about last night.
Oh my, I was wondering what all of the birds do in this situation we find ourselves in here in Western NY. Thanks for enlightening me and I feel really bad for the birdies at the bottom of the box, sniff. So many questions about nature.
5 April 2007 at 8:57 pm
Do not apologize for rambling because in this situation, I’d ramble, too. I don’t know what the line of interference is, but I’d want to rescue those in danger of suffocating. I’m not a biologist, though. That swallow peeking at you is priceless. I was also surprised that so many of the southern migrators don’t make it back. Keep rambling, Tom. We all need to learn from it.
5 April 2007 at 10:19 pm
Very interesting post, Tom. I saw tree swallows here this week as well and our temperature today was -9C with heavy snow and high winds. Nature can be harsh. The later migrants will have to make up for those who did not survive this spring storm.
5 April 2007 at 11:18 pm
I have been worried about my TRES. I haven’t seen them since the temps fell two days ago.
In a world without nest boxes, would they all pile into a natural cavity and suffocate?
It’s a sticky wicket, caring about feathered family members. We put up boxes, and when Nature does Her thing, we have to decide how much to intervene.
No worries about the ranting. I lay in bed thinking the same things as you.
5 April 2007 at 11:49 pm
I can understand the concern. The only biology class I ever did was a birding course, and the text book was the same by Frank Gill. One of the assignments was about survivability – birds really have a hard life… but are so admirable (most) in their parenting concerns and effort.
5 April 2007 at 11:50 pm
It’s so hard to just let nature *be* – isn’t it. I tell myself that they’re *professional* birds and know what’s best and try not to worry over it too much.
Tree swallows arrive early and often suffer for it. I’ve seen it here in NJ too. But they keep doing it, so there must be some benefit, otherwise it wouldn’t continue.
Your photos are wonderful tonight – maybe that’s enough for their early arrival.
6 April 2007 at 12:06 am
It’s so different in different parts of the country too. Our swallows are living it up in bug heaven here. I killed my first mosquito today. Wonderful thoughts!
6 April 2007 at 12:24 am
-Interesting topic-the kind I would look for in a birdig magazine but with your own touch.-Love the picture of those bug-eyes.
6 April 2007 at 6:18 am
It’s so hard to just let nature *be* – isn’t it. – I agree with Laura. I’ve gone through a lot of introspection about feeders, especially after the October Storm. Are we enabling or empowering?
It is part of our nature to help out a creature in distress. In fighting off our own nature, do we contribute something or take something away? If a bird who’s smart enough to be injured in view of humans ends up surviving to fledge other smart birds, has selection worked?
I guess you have to go with your heart. If you are collecting data or doing other journalistic work, maybe you have to walk away. If you are out walking and enjoying, maybe you can step in? This is what anyone (like myself) struggles with who does what they love for a living. When am I on and when am I off? The very fact that anyone thinks about this stuff adds to my respect for them.
6 April 2007 at 8:44 am
I enjoyed your ramblings…..You do a great job and service (I love to see a person enjoy his/hers profession.
6 April 2007 at 11:29 am
Nature can be very cruel, at least by human standards. That’s one reason why I am not working in any wildlife field–I would want to be out rescuing whatever.
6 April 2007 at 1:13 pm
@ Nature Woman – They do their best to survive! Thanks
@ Mary- you ramble? Thanks for such kind words and not much I could really do for them! Ugg
@ Ruth Thanks and hope your birds are doing alright! ugg,
@ Susan – how do we ever get to sleep at night? Lucky your group is able to do things for the raptors!
@ Shutterbug – thanks and I agree! It is a great book! Hope you still use it? I do!
@ Laura – thanks for such kind words and sorry to hear about your swallows also!
@ Liz – good reasons I would love to come south for the winter?
@ Larry – thanks for such kind words! 🙂
@ Jen – Thanks and what you say means alot!
@ Jim – thanks and glad you enjoy this!
@ KGMom – Ugg, but my overall goal is to do my best for protecting them (as a hole)!
THANKS EVERYONE! You all are soo kind!
6 April 2007 at 8:31 pm
My heart breaks for the ones on the bottom.
12 April 2007 at 9:44 pm
Barb, I am so afraid to check the boxes, I hope I am wrong!
13 April 2007 at 10:31 am