Showing posts with label Bird nest. Show all posts
Showing posts with label Bird nest. Show all posts

Tuesday, March 3, 2015

Bird Nest Design



Bird Nest Design - More Complex and Fascinating than you Ever Would Have Suspected




Nest design in birds is fascinating, and not just because it's, well, er, fascinating, but also because studying it forces us to rethink what we've assumed to be true. Science is, in spite of what we'd like to think, rife with assumptions. Luckily, most of these assumptions are small, insignificant, and don't influence many decisions. But, alas, they are there, and they're often cryptic. Clearing out that ambiguity can be a challenge, but when done as part of the quest to find truth rather than to be proved right, the results can be breathtakingly interesting.

Such is the case in a recent "review" paper called The design and function of birds’ nests. In this paper, the authors have systematically sleuthed through their own and a great variety of other authors' research to produce a succinct, and elegant, set of overarching themes. Quick digression. Why do I love these kinds of papers so much? If one is researching a topic, typically he/she would have to hop between a great number of potentially unconnected papers, hoping to draw the right conclusions between them all. In review papers, fulltime, professional scientists have done that for you, and they've done it with access to more research, more great minds, and more cutting edge ideas. In short, they're laying out all the research--and with it the prevailing ideas--on a particular subject for your convenience. It's good stuff.

Anyway, back to the research. In birds, there's a significant behavior that we--lay people and ornithologists--take for granted all too often: the nest. In ornithology, the prevailing assumption has been that nests are purely used by birds for nesting and nothing more. More specifically, the assumption is that nest design--and time spent building--is determined purely by natural selection, with the selective pressure, of course, being predation risk.

But there are lots of strange behaviors, found both in observational and experimental studies, that challenge seemingly obvious assumption. The best part? There are a lot of questions left to be answered. Let's dive into some of the interesting bits (read as much or as little as you please):

Nest site selection is highly influenced by predation risk. Interestingly, birds who nest high in the forest strata are at greater risk of predation from avian predators, but much lower risk from mammalian predators. Conversely, birds that nest low in forest strata are at high risk from mammalian predators and low risk from avian predators. Birds nesting halfway up are at equal risk from both. So (#FieldSkills), if you're in an area where most of the bird species nest high, for example, it can be reasonably assumed that mammalian predation is more prevalent than avian predation. There are some other interesting observations from studies on nest placement in relation to predation risk:

Some birds nest near wasp nests or other aggressive species like kestrels to reduce risk of predation, even if it puts them in a certain amount of danger

Some birds will actively shift their nest site halfway through the breeding season if the previous site proved to be rather predator-laden. This is interesting because it indicates that nest site selection is not purely genetic/instinctive, but rather that it is a combination of instinct and learning.

Some birds will even track the amounts of rodents in their area and colonize more heavily in areas with heavy rodent concentrations. They do this because species that would prey on them prefer rodents, and with heavy rodent population, the predation risk is lower.

Ground nesting birds instinctively "know" the color of their eggs and actively seek potential laying areas where their eggs will blend in

Nests can be used to express the fitness of a potential mate...in other words, nest design is also subject to sexual selection (BIG IDEA)

Sexual selection favors larger nests, able to house more eggs. This is in direct contrast to natural selection for small nests.

Birds with high body condition invest more in nest building, indicating that the quality of a male's nest can be used by the female to gauge the quality of the male as a mate.

Male starlings integrate green plant material into their nests, and females respond by integrating feathers into the same nest. This is fascinating because it indicates that females are "impressed" by male presentation of green plant material, and are actively responding by investing more in the nest.

Birds change their nesting habits with altitude as well. Nesting high in trees, and thus closer to the sun and its head, is common in high-altitude species. These nests average more insulated as well to account for more radical changes in temperature.

A quick look at the paper.

These points are only the tip of an iceberg of interesting information in this paper (which, by the way, is open access...click the image to the right!). The most important overarching theme is this: nest design is subject to natural selection AND sexual selection. An inconspicuous nest can hide chicks from predators, but it may also leave females unimpressed. Birds designing nests have a lot to take into account to protect offspring: microclimate, color of the environment, parasites, what nest insulation is necessary, how impressive a nest may be to the opposite sex, etc. And all this is reflective of the health (quality) of the nest site selector and builder.

I don't know about you, but this stuff gets me excited. There are so many little details, so much nuance, that remind us of the staggering complexity of the world around us. What a privilege it is that we can even begin to figure it out.

I encourage you all to read the paper yourselves, and, as with any perpetual learner, to ask as many questions as possible. This paper does a good job of highlighting what's yet to be learned; seize that opportunity!


Bird Nest Design



Bird Nest Design - More Complex and Fascinating than you Ever Would Have Suspected




Nest design in birds is fascinating, and not just because it's, well, er, fascinating, but also because studying it forces us to rethink what we've assumed to be true. Science is, in spite of what we'd like to think, rife with assumptions. Luckily, most of these assumptions are small, insignificant, and don't influence many decisions. But, alas, they are there, and they're often cryptic. Clearing out that ambiguity can be a challenge, but when done as part of the quest to find truth rather than to be proved right, the results can be breathtakingly interesting.

Such is the case in a recent "review" paper called The design and function of birds’ nests. In this paper, the authors have systematically sleuthed through their own and a great variety of other authors' research to produce a succinct, and elegant, set of overarching themes. Quick digression. Why do I love these kinds of papers so much? If one is researching a topic, typically he/she would have to hop between a great number of potentially unconnected papers, hoping to draw the right conclusions between them all. In review papers, fulltime, professional scientists have done that for you, and they've done it with access to more research, more great minds, and more cutting edge ideas. In short, they're laying out all the research--and with it the prevailing ideas--on a particular subject for your convenience. It's good stuff.

Anyway, back to the research. In birds, there's a significant behavior that we--lay people and ornithologists--take for granted all too often: the nest. In ornithology, the prevailing assumption has been that nests are purely used by birds for nesting and nothing more. More specifically, the assumption is that nest design--and time spent building--is determined purely by natural selection, with the selective pressure, of course, being predation risk.

But there are lots of strange behaviors, found both in observational and experimental studies, that challenge seemingly obvious assumption. The best part? There are a lot of questions left to be answered. Let's dive into some of the interesting bits (read as much or as little as you please):

Nest site selection is highly influenced by predation risk. Interestingly, birds who nest high in the forest strata are at greater risk of predation from avian predators, but much lower risk from mammalian predators. Conversely, birds that nest low in forest strata are at high risk from mammalian predators and low risk from avian predators. Birds nesting halfway up are at equal risk from both. So (#FieldSkills), if you're in an area where most of the bird species nest high, for example, it can be reasonably assumed that mammalian predation is more prevalent than avian predation. There are some other interesting observations from studies on nest placement in relation to predation risk:

Some birds nest near wasp nests or other aggressive species like kestrels to reduce risk of predation, even if it puts them in a certain amount of danger

Some birds will actively shift their nest site halfway through the breeding season if the previous site proved to be rather predator-laden. This is interesting because it indicates that nest site selection is not purely genetic/instinctive, but rather that it is a combination of instinct and learning.

Some birds will even track the amounts of rodents in their area and colonize more heavily in areas with heavy rodent concentrations. They do this because species that would prey on them prefer rodents, and with heavy rodent population, the predation risk is lower.

Ground nesting birds instinctively "know" the color of their eggs and actively seek potential laying areas where their eggs will blend in

Nests can be used to express the fitness of a potential mate...in other words, nest design is also subject to sexual selection (BIG IDEA)

Sexual selection favors larger nests, able to house more eggs. This is in direct contrast to natural selection for small nests.

Birds with high body condition invest more in nest building, indicating that the quality of a male's nest can be used by the female to gauge the quality of the male as a mate.

Male starlings integrate green plant material into their nests, and females respond by integrating feathers into the same nest. This is fascinating because it indicates that females are "impressed" by male presentation of green plant material, and are actively responding by investing more in the nest.

Birds change their nesting habits with altitude as well. Nesting high in trees, and thus closer to the sun and its head, is common in high-altitude species. These nests average more insulated as well to account for more radical changes in temperature.

A quick look at the paper.

These points are only the tip of an iceberg of interesting information in this paper (which, by the way, is open access...click the image to the right!). The most important overarching theme is this: nest design is subject to natural selection AND sexual selection. An inconspicuous nest can hide chicks from predators, but it may also leave females unimpressed. Birds designing nests have a lot to take into account to protect offspring: microclimate, color of the environment, parasites, what nest insulation is necessary, how impressive a nest may be to the opposite sex, etc. And all this is reflective of the health (quality) of the nest site selector and builder.

I don't know about you, but this stuff gets me excited. There are so many little details, so much nuance, that remind us of the staggering complexity of the world around us. What a privilege it is that we can even begin to figure it out.

I encourage you all to read the paper yourselves, and, as with any perpetual learner, to ask as many questions as possible. This paper does a good job of highlighting what's yet to be learned; seize that opportunity!