Tag Archives: grassland birds

Why Are We Spending So Much Time Studying Birds?

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Believe it or not, I really do like birds.

(And thus starts another blog post destined to draw the ire of my ornithologist friends…)

But here’s the thing.  I just read yet another study of grassland birds in which the researchers looked at the relative importance of variables such as habitat structure (tall, medium, and short grass, amount of shrub cover, etc.) and landscape composition (how much grassland is in the landscape).  It was a nicely designed study, but I found myself wondering how much value these kinds of studies are really adding to our ability to do effective grassland conservation.

A dickcissel sings from the top of a Woods' rose in restored Platte River prairie. Compared to most other kinds of animals and plants, we have a pretty solid understanding of the breeding habitat requirements of dickcissels and other grassland breeding birds.

Yes, we still have a lot to learn about grassland birds and their habitat requirements.  The more we learn, the better able to design conservation actions to help birds.  On the other hand, we already know an awful lot about grassland birds relative to other groups of grassland species like snakes, ground squirrels, grasshoppers, leafhoppers, fungi, and nematodes.

It’s kind of like we’re going to high school but only really studying in art class.  Art is important and enjoyable, but focusing only on art is not going to prepare us very well for dealing with the world.

If I was going to design a grassland landscape to maximize bird conservation, I think I could do a pretty good job based on what we know right now.  I’d start with multiple large blocks of prairie (hundreds of acres in size – much bigger, if possible).  Those blocks of prairie would need to include both upland and lowland grassland areas, and be floristically diverse enough to support an abundant supply of insects and seeds.  I’d include some scattered patches of shrubs and small trees in the landscape, but would place them so that there are still large areas of grassland with no woody vegetation at all.  Management would be important, and I would try to ensure that a variety of habitat structures was available each year, including the whole continuum between very short-cropped vegetation and tall dense and/or weedy cover.  It would be great to have those habitat types mixed together such that each block was a decent size (20 acres or more?) but that they were close enough together that birds species requiring more than one cover type during a season can easily move between them.  I’m sure those more up to speed on current literature might add a few tweaks to this landscape design, but I think this covers the more important components.

Sure, there are still a few holes in our knowledge of, especially in terms of their requirements for migratory habitat, but as a whole we’re in pretty good shape.  I would argue that our biggest limitation is not the ability to predict what birds need, but rather our ability to implement the necessary changes on the land.  However, that only applies to birds.  Does anyone feel they could similarly and accurately predict the landscape scale habitat needs of the smooth green snake, Franklin’s ground squirrel, or the long-jawed orbweaver spider? Not me.

A smooth green snake found in the Platte River Prairies, Nebraska. Very little is known about the habitat and/or landscape requirements of species like this one. We don't even really know much about how many there are. They are considered to be rare in most places, but we find them fairly regularly in our prairies - they're just really hard to see!

It would be different if we were confident that a landscape designed for birds would provide for the needs of all other prairie species.  I think we’re far from being able to say that.  Here’s just one reason I’m skeptical:  Grassland bird species are extremely mobile, and most migrate long distances between breeding seasons.  This allows those birds to find the best appropriate habitat (within reason) each year, even if that habitat isn’t where it was the previous breeding season.  Most other grassland species don’t have that kind of mobility, but many (most?) of them have fairly specific habitat structure requirements.  When the habitat structure where those species are living changes, how far can they travel to find appropriate habitat?  What kinds of terrain can they cross?  These are questions with huge implications for how we should be managing prairies and prairie landscapes, but we can’t do anything but make wild guesses because although we know how birds deal with those issues, we don’t know how most other species do.

I explored this issue of birds as indicators for the conservation needs of other species in an earlier post, if you’re interested in reading more.

Mice are fairly mobile species (compared to wingless invertebrates, for example) but we still know relatively little about their ability to find the kinds of habitat structure they need. When conditions change, do they travel long distances in search of appropriate habitat? Or do they just hunker down and wait for better times? If they travel, how far can they go, and what challenges do they face?

So why are we still spending so much time studying birds instead of branching out to other species and broader questions?  One big reason is inertia.  Scientists rightly like to build upon previous projects, so because there have already been a lot of studies of birds, there is a lot to build upon.  This makes sense in terms of efficiency (study methods are already designed and tested) and from the standpoint of funding availability (it’s often easier to sell a project that is builds upon what we already know than one that is reaching into the unknown).

A second reason we study birds so much is that they’re relatively easy to see, hear, and identify.  Since most research is done by graduate students and technicians, picking species that can be learned quickly is very helpful.  I should know – I did my own graduate research on grassland birds!  However, since then, I’ve learned that it’s not that hard to pick up on the sampling and identification skills needed to study other organisms, and that with invertebrate species, there are experts that can do the identification for you.

Of course, the biggest reason we study birds so much is that we LIKE birds so much.  If ground beetle watching was as popular as bird watching, prairie research and conservation efforts might look very different!  The irony, of course, is that we’re essentially focusing a very large proportion of our research and conservation effort on only a dozen or so grassland bird species (in any particular landscape).  At least if we were studying ground beetles, we’d be looking at several times that many species – and while I don’t know that much about ground beetles, I’ll bet they would be equally good indicators of the “health” of the prairie ecosystem.

A sedge wren on velvety gaura in the Platte River Prairies. Tiny birds, with cute little tails and aggressive personalities, sedge wrens are great examples of why birds are so compelling to people.

Look, I get it.  We’re not going to turn this battleship on a dime and move all the bird research funding and effort into smooth green snake and ground beetle research within a year or two.  However, I do think it would be really valuable for those doing bird research to incorporate broader community questions into their projects, whenever possible.  Maybe we could start by asking questions about how well birds really do represent the needs of other species?  Would funders of grassland bird research be open to that line of exploration?  It would allow us to build upon what we know about grassland birds by testing those known parameters on other taxa.  If we could figure out where the needs of birds and other species diverge, that’d be a great step forward in terms of defining future research needs.  Are great prairie chicken landscapes also great grasshopper landscapes, or not necessarily?  Do sedge wrens and massasaugas have similar habitat needs, or at least compatible habitat needs?  If not, how do we balance the needs of both species?  Let’s build on what we know about birds, but do it through some comparative analyses with other species.

Because you’ve got to admit – ground beetles are pretty cute too!

Ground beetles like this one (Pasimachus sp?) are abundant and diverse members of the prairie community. What do we know about their conservation needs? Not much.

What Do Grassland Birds Need for Migratory Habitat?

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A new study sheds (a little) light on a slice of grassland bird life we know very little about.

We know a lot about grassland birds.  Sure, there’s a lot we don’t know too – but we certainly know a lot more about grassland birds than we do about leafhoppers, nematodes, or most other groups of grassland species.  So how is it possible that we know almost nothing about what kinds of habitat grassland birds need during migration?

Do lark sparrows look for the same habitat during migration as they use for nesting? We really have no idea.

I’ve wondered about this for a long time – ever since I did my graduate work on grassland birds back in the 1990’s.  At that time, I was one of a growing number of researchers investigating the importance of the size and shape of prairie habitats to grassland birds.  We now know that prairie size and shape are very important, and more recent studies are even showing that the amount of grassland in the neighborhood around a particular prairie influences whether or not grassland birds will nest there or not.  As we continue to refine our understanding of breeding habitat needs, however, we’ve made no significant progress at all on what grassland birds need for habitat during migration – even though we know that migration is an incredibly stressful part of a bird’s life cycle.  It’s reasonable to wonder, in fact, if population declines in many grassland bird species could be more strongly tied to migratory and winter habitat than to breeding habitat.

For more than a decade, the only available published information on habitat use by grassland birds outside of their breeding areas has been a very nice study of winter habitat use in south Texas from 1999.  That research found grassland birds using a much broader array of habitat types than expected, including brushy and even woodland habitats.  The authors, however, were quick to point out that just because birds were using particular habitats doesn’t mean that those habitats were preferred, and there is no data on how well birds were doing in those habitats.  Still, it’s intriguing to think that bird species that are so picky about finding big open grasslands for nesting might not hang around in the same habitat types at other times of the year.

Just last week, I talked to one of the authors (Patrick Doran, The Nature Conservancy – Michigan) of a new paper that gives us our first real peek into the migratory needs of grassland birds.  Bruce Robertson, Doran, and others conducted a study of how grassland birds utilize grassland and biomass crops as migratory habitat as part of a larger project to assess biomass crops and their potential impact on birds in Michigan.  Their data on bird use of switchgrass fields and prairies during migration showed that obligate grassland birds (species that rely solely on grasslands for breeding habitat) were positively tied to large grassland patches and tended to stay away from wooded areas.  In addition to those two variables, obligate grassland birds also tended to use grasslands with patchy vegetation structure (a mixture of tall and short structure) more than uniformly tall/dense grass.

Large prairies with heterogeneous vegetation structure may be favored by migratory grassland birds. In August and September, as many grassland birds are moving south, both seeds and insects are abundant in many prairies. Is one food source more important than the other? Is either important? Or are birds simply looking for a safe place to rest before continuing south?

This project was a great first step, but like all good research projects, it left us with more questions than answers.  What are those grassland birds using the habitat for?  Are they feeding significantly while there or just resting?  If they’re feeding, are they eating insects or seeds – or both?  Do grassland birds look for the same habitat structure (e.g., tall/dense or short/sparse, etc.) when choosing migratory stopover habitat as they do when choosing breeding habitat?  Knowing the answers to those questions would sure be helpful as we think about how to manage prairies.  For example, assuming habitat structure is important to grassland migrants, decisions whether to burn a prairie in the fall, early spring, or late spring could have very big implications for migratory birds.

One of the most interesting findings in the study by Robertson and his colleagues is the suggestion that grassland patch size might be important for migratory grassland birds.  Woodland migrants have been more extensively studied than grassland birds, and while the picture is not yet clear, it doesn’t appear that birds that require large woodlands for breeding habitat necessarily require the same for migratory stopover habitats.  As an example, a study in eastern South Dakota found that neotropical migrants seemed to use small farmstead woodlots and large Missouri River woodlands interchangeably.  Again, there are still lots of questions still to answer (e.g., are there differences in stress levels or weight loss between habitat types?) but that apparent ability for woodland birds to feed and roost in small woodland habitat during migration has important implications for conservation.  If larger woodlands were required for migratory stopover sites, our challenge to provide appropriate habitat would be much more difficult – especially in landscapes like those in North America’s Great Plains.  It looks like we might not get off so lightly in the case of grassland birds.  If this recent study is representative, the future of grassland bird populations may hinge on our capacity to increase the number of large (how large is large enough??) grassland habitat patches in our most fragmented landscapes.

I’m hoping that the study by Robertson and his colleagues will spawn others like it.  However, studying migratory grassland birds is difficult.  How many of you are comfortable identifying little brown grassland birds when they don’t sing – and when your only look at them comes as they are darting away from you and diving back into the grass?  Regardless of the difficulty, though, we really need the information, and that information doesn’t have to come soley from academic research.  Any birdwatcher or prairie manager could add critical information to what we know by simply keeping track of the grassland bird species they see during spring and fall migration, and noting any habitat characteristics they can (e.g., prairie size, distance from trees, habitat structure – tall, short, dense, sparse).  At worst, sharing field notes with each other might give us at least something to go on as we think about management, and at best could provide pilot data to help design more effective research projects than could be designed by starting from wild guesses.

It seems reasonable to expect that late summer haying reduces the quality of prairies for migrating grassland birds. On the other hand, maybe not?

Our Platte River Prairies are located just to the south of an incredible grassland landscape – the 12 million acre Nebraska Sandhills.  I sometimes wonder about the birds that nest there.  They aren’t lacking for breeding habitat quantity or quality, as far as we know, but they’re only in those big sandhill prairies for a small proportion of their year.  In order to survive to the next breeding season, those birds have to make their way south through some very fragmented landscapes, survive the winter in what can be perilous southern habitats, and then work back north through those fragmented landscapes again.  Our Platte River Prairies are probably among their first stops heading south and their last stops heading north.  Are there management practices that we’re doing that are contributing positively or negatively to the success of those migratory birds?  We really have no idea.  That makes me uncomfortable.

I imagine the birds are a little nervous too.