Archive for April, 2012

At the edge of a parking lot, here in Davis, CA, my wife and I found a family of Killdeer.  The two adults were wandering around a patch of dry, exposed dirt and watched over their four young as they also wandered the dirt patch foraging for food.  Killdeers clutches are usually comprised of four eggs, so this looks like it was a very successful nest where all four eggs hatched and the young all seem to be doing quite well.  The young were tiny balls of fluff on legs that seemed too tall for them (it will be a little while before they grow into them).  Their coloration was an almost exact replica of the adults: brown back, white belly, and the classic black ring across the neck.  The young birds only had a single ring and will get their second when they molt into their first basic plumage.  At one point, one of the young gave a call that sounded exactly like that of an adult bird.  It was impressive to hear this bird, that could not have been more than a few days old, already able to produce fully developed vocalizations.

The young, being highly precocial and so able to walk as soon as their feathers dry, were wandering over a good sized area.  One in particular was exploring and foraging much farther away from its parents then its siblings.  I wonder if this more adventuresome behavior will be a consistent aspect of this bird’s personality, and also if this personality continue into adulthood?  Personality, or behavioral syndromes as they are often called, have been found in many species, but little work has been done on when these behavioral syndromes form or how they may change as an individual ages.

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The birds of prey, here in Davis, are in full nest-building mode.  Yesterday I followed an adult, light morph Swainson’s Hawk that was carrying a stick and so found my first Swainson’s Hawk nest of the year being built near the top of a redwood tree on campus.  This is the exact spot where a pair nested last year and is also where I saw my first Swainson’s Hawk this year.  I have no idea if this is the same pair that held this territory last year, but it does seem likely.

Additionally, today I saw a White-tailed Kite in some grasses on the ground.  As I watched, it took off with a bundle of dead grass in its beak.  I was able to follow this bird to my first White-tailed Kite nest of the year.  This nest is in the very top of a Valley Oak out near my lab.  The tree is along a ditch that acts as a riparian corridor, although there is no water on the surface, through the otherwise agricultural land that fills the surrounding area.

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Each year, the American Birding Association (ABA) selects a particular species as its Bird of the Year.  The species is selected based on a combination of character of the bird itself, how it related to birders, and how it can serve as a symbol for the birding community.  This year, the ABA Bird of the Year is the Evening Grosbeaks, and as I have been studying Evening Grosbeaks for the past three years, I was especially excited by this choice.  I figured the added attention on this species might lead people be curious to know about them and their biology, and so here is a bit of information on them.

Evening Grosbeaks are a fascinating species for many reasons.  One of these reasons, and the one that first caught my attention, is that there have been so few studies done.  For being so common a visitor to backyard bird feeders, especially in winter, I was amazed at how little was known about these beautiful birds.  Do Evening Grosbeaks have a song?  What do the courtship rituals involve?  How many subspecies exist?  Where do birds go to throughout the year?  How do birds find food sources?  All of these are big unknowns for the Evening Grosbeak, and that intrigues me.

But before we get into more of the unknown, here is some of what is known about this bird.  It belongs to a group called the Cardueline Finches.  This group includes such species as House, Cassin’s and Purple Finches; Pine Grosbeak; the Goldfinches; the Crossbills; the Redpolls; and all the Siskins.  This group is found across North and South America and Eurasia.  Many of these species do not have regular migratory routes, but are referred to instead as nomads.  Unlike many birds, which have breeding grounds where they can be found in summer and non-breeding grounds where they can be found in winter, nomadic species move across the landscape to follow food resources wherever they happen to be.  This means that where groups of birds are to be found at any given time of year can be very unpredictable.  They seem to congregate where there are large concentrations of food, although how they find their food is a mystery.  For the Evening Grosbeak, these food resources are usually large insect outbreaks or areas where the coniferous trees have big crop of cones.  Other foods that Evening Grosbeaks seem to like are the Safflower and Black Oil Sunflower seeds they find at bird feeders.  One interesting dietary foible is that they seem to have a strong affinity for salt.  They have commonly been reported coming down to drink from mineral springs, and also have been shown to prefer soils that have had salt added over soils that have had nothing added.

Geographically, the Evening Grosbeak has been expanding its range into the eastern United States in the past hundred years or so.  The first recorded sighting of an Evening Grosbeak in New England came in the 1890s, and the first breeding record was in 1940.  One thought as to why this eastward has been taking place is the extinction of the Carolina Parakeet.  When the Carolina Parakeet, North America’s only native parrot, was alive their diet consisted predominantly of large seeds.  When they were driven to extinction, this food resource was left open, and the Evening Grosbeak had the equipment to break into such seeds as Bald Cypress cones which other birds were too small to tackle.

The number of subspecies of Evening Grosbeak has been a developing story since the late 1800s and has had its’ fair share of confusion.  In 1874 a natural historian, Ridgeway, found that birds in Mexico looked different from the birds he was used to seeing in the eastern United States. The yellow eye-stripe of the male Mexican birds was longer and wider than eastern birds and the bills were longer, wider, and less curved.  This led him to separate birds in the western half of the continent from the birds in the eastern half of the continent thereby creating two subspecies.  In 1917, Joseph Grinnell at the Museum of Vertebrate Zoology at the University of California, Berkeley, took a closer look.  He noticed that the birds that Ridgeway had found were representative of the birds in Mexico, but that they were subtly different from birds found in other parts of the western US.  Grinnell agreed that the eastern birds represented one subspecies, but he separated the birds in the western US into four subspecies based on differences in plumage color and brightness, and slight differences in bill shape and size.  The resulting five subspecies were the accepted taxonomy until 1957 when the American Ornithologists Union decided that the slight differences in bill shape and size that Grinnell had described were not enough to warrant subspecies status for some of these populations.  Instead, they settled on three subspecies.  The eastern birds represented one subspecies, as everyone agreed, the birds from Mexico represented a second, and birds from the rest of the western United States represented a third.  Since 1957, these subspecies have been the three to have accepted taxonomic status.

Regardless of how many subspecies exist, some people have taken notice of trends that stretch across the whole species.  One disturbing trend was found by scientists at the Cornell Lab of Ornithology who examined Christmas bird count and breeding bird survey data and found that numbers of Evening Grosbeaks have been declining across the country. Over the past two decades, Evening Grosbeaks have been seen at fewer and fewer sites.  Additionally, the sites that still have their Evening Grosbeaks have been observing smaller and smaller flocks.  Since these birds are so unpredictable in their movements, and they frequently live in the back country where Christmas bird counts are rare, it is possible that the birds are simply going to places where they are not being seen.  However, since the Cornell scientists only found declines all across the country, and found no population increases even at small local locations, the continent wide population decline seems like a real possibility.

In terms of vocalizations, Evening Grosbeaks present other interesting traits.  Evening Grosbeaks have a number of vocalizations.  One kind of vocalization is the flight call.  This is a short, single-note call that seems to function in flock movement coordination.  This call has been observed to vary from population to population in different parts of the country, and the different variations seem to be quite distinct.  Each variation was called a Type and given a different number.  So, now different birds have been identified as producing Type 1 flight calls or Type 2 flight calls all the way up to Type 5.  No bird has ever been found to make more than one Type of flight call, but birds that produce different flight call types do sometimes occur in the same place at the same time.  Interestingly, when the distributions of these different flight call Types are mapped across the continent, they match where Joseph Grinnell mapped out his five subspecies!

So what is going on here?  Can birds use flight calls to identify other individuals such as their mate?  Do they prefer to associate with other birds that make the same type of flight call?   Do the different flight call types play a role in choosing a mate?  Do birds that make different flight call types prefer different sized seeds?  Are the birds that make different flight call types genetically different as well?  How are the differences in flight call types able to persist when these birds move around and overlap with each other?  These, and other questions, are what I hope to find out.  So do you have Evening Grosbeaks, the ABA Bird of the Year, coming to your feeders?  Let me know, and I will report back on what I find!

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There is a post doc working for my adviser who is from Glasgow, Scotland, named Lindsay.  She and I have been comparing birds in North America to their counterparts in Europe.  One especially interesting example to me was the Northern Harrier of North America and the Hen Harrier of Europe.  These birds are considered different species by some and different subspecies of the same species by others.  The reasons for having some kind of distinction between the two populations usually rests on the fact that they are separated by an ocean and also on slight differences in size.  However, we being students of behavior, Lindsay and I were talking about behavioral differences between the two, and there was one that really jumped out at us.  She was surprised to see so many harriers in the agricultural land around the town of Davis.  In Scotland, the Hen Harrier generally keeps to more natural landscapes of moor and meadow.  Here in the U.S. The Northern Harrier is a common sight in human dominated landscapes such as empty lots and agricultural fields.  In fact, they even breed in these fields fairly frequently which was quite a surprise to my Scottish friend.  This demonstrates how important the study of behavior can be.  The outward, physical differences between birds from these two populations are slight, but they have these distinct behavioral differences in where they hunt and where they breed.  Surely this kind of information could , and should, be used when defining species!

I want to collect such differences in behavior between different populations, so do you know of any?  They can be from any continent or any combination of continents, and involve any species.

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Today, on the U.C. Davis campus, I found a female Brewer’s Blackbird gathering nesting material.  She picked up bits of grass and other debris, including a bit of paper that looked like a gum wrapper, until her beak was full and bits of grass were falling out of the sides.  When she took her load up into an ornamental juniper that is growing in the open area between two buildings where people lock up their bikes.  The nest is about half way up the tree (which is only about 20 ft tall) and deep enough in the foliage that it is not visible from the ground.  Talk about a species that is tolerant of close contact with humans!  People were walking right past the base of the nest tree, talking and laughing, and this did not seem to deter the nesting blackbird at all.

Today, I also saw my first Wilson’s Warbler of spring.  I know they have been in the area for a little while now, but this beautiful adult male was the first one I have actually crossed paths with.

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Today there were lots of Ladybird Beetle larva roaming around on the leaves of several of the bushes in my neighborhood.  They must have been hatching just recently, because I have not been seeing any at all before today.  The Ladybird Beetle (commonly called a ladybug, even though it is not a true bug) is a member of the family Coccinellidae.  This is a family with over 5000 specie world wide, and some members found on every continent except Antarctica (North America has about 450 native species).  The larva have somewhat spiky bodies that are black with red markings on the sides.  They metamorphose into the familiar adult beetles that have brick red backs with black spots.  Interestingly, the adults of many species are plain green when they first emerge, and the red and black coloration develops as the exoskeleton dries and hardens.  A bit of insect trivia for you.

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One of the reasons that I started this blog was to help myself clarify my own thoughts, and discuss my own research plans (see my About section).  This post is the first such entry.  As a graduate student, I am constantly being asked by professors how my research fits into the bigger picture of biology.  Why is what I am doing worth while?  There is a professor here at U.C. Davis who frequently asks all sorts of people “if I don’t care about (insert whatever the person studies here), and I don’t, why should I care about your research?”  It is a good question.  What is the broad implication and value in why we are doing what we are doing?  So here is my answer to this question, as it stands now.  I am sure this will change and evolve as I progress through my research, but for now, here goes…

I have been thinking a lot about how the study of animal behavior can contribute to the conservation of those animals and to biodiversity in general.  Conservation is a pretty big issue, and the connection between animal behavior and conservation is a pretty under-explored area of thought, and it seems to me to be a pretty important one.

The first connection that occurred to me was an extension of the Endangered Species Act of 1973.  The Endangered Species Act (ESA) calls for the protection of any and all species that are declining and/or in danger of extinction.  The ESA defines a “species” as a species, subspecies, or distinct population that contains a significant portion of the species evolutionary heritage.  This is a pretty broad definition of a “species,” and is certainly not how biologists use the term, but for legal reasons, that is the way the law was written.  It seems to me that, with this broad definition, the study of animal behavior can provide useful knowledge to the implementation of the ESA in two areas.  One is a matter simple identification.  Different populations, subspecies, or species can be identified by behavior.  The flycatchers in the genus Empidonax, for example, look very similar to one another and can only be reliably identified by vocalizations or by catching them and taking careful measurements.  Some members of this genus are is conservation concern and others are not, so being able to distinguish between them is essential.  So, determining which behaviors are useful for distinguishing different species, subspecies, or populations can be an important contribution from the discipline of animal behavior to conservation.  My second area revolves around the idea of certain populations representing unique and important aspects of a species’ evolutionary potential or heritage.  What makes a certain population different from any other?  Is it just that they, perhaps, live in a different location?  This geographic distinction is the most commonly used yardstick for designating populations as being worthy of protection under the ESA, but I do not think it is the only yardstick.  I don’t even think it is the most important.  If animals that are members of one population do something that is different from another population, be that they eat a different food or breed in a different part of the habitat or move to different areas when they migrate, this difference represents an important innovation.  It is exactly these new innovations that allow species to adapt to fill new niches in their environment and evolve.  The identification of unique, behavioral innovations in another way that the study of animal behavior can influence the interpretation of the ESA and so affect conservation.

A third idea on this subject was presented to me from a professor here at U.C. Davis.  It is the idea of behavioral diversity.  Having many individuals in a population makes it more likely that different individuals will develop different skills and abilities.  This is a simple numbers game, where to larger the population, the larger the number of behaviors that will be found in that population.  Preserving as many different behaviors as we can will make it more likely that populations will be able to accommodate any changes that arise (these changes could be in the form of climate change or an invasive species or urbanization or anything else).  Here again, studying animal behavior can show us how many behaviors exist, how common each behavior is, and which members of a population do each one.  Knowing this can give those who work in wildlife management a better understanding of what they need to preserve to make the long term survival of a species more likely.

So, are you convinced?  Do you see that there is a connection between animal behavior and conservation, and do you agree that it is an important connection?

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When I began to study Evening Grosbeaks, three years ago, my adviser and I talked a great deal about how to go about studying these birds.  He, and most of the rest of the members of his lab, study the Cardueline Finches which is a group that contains such birds as the House Finch, siskins, goldfinches, redpolls, and crossbills in addition to the Evening Grosbeak.  Most of these birds are more or less nomadic which means they do not follow a standard migratory pattern.  Many birds have a breeding area and a non-breeding area, and they migrate back and forth between these places each year.  Not so for the Carduelines.  Instead, Cardueline Finches seem to follow food sources wherever they pop up.  Big groups of these birds will settle in to an area of forest where the coniferous tree are having an especially good cone crop.  They will stay and breed there for a while, but then pick up and leave when the food starts to run out.  This means that it is very hard to predict where groups of these birds will be at any given moment which makes then quite challenging to study!  My adviser explained his strategy to me which he has used with success.  It basically involves a great deal of time wandering about in the mountains hoping to cross paths with a flock.  I was working on a Master’s degree, then, and did not have enough time to devote to this kind of hopeful wandering if I was going to finish my degree on schedule.  But I knew something that no one else in the lab seemed to know: I knew birders!

Since I have been one all my life, I knew that there were birders out there who were very dedicated in in keeping their feeders filled with seed.  I knew that there were birders out there who kept extensive records of what came to their yards or what could be found in the areas around their homes.  I knew that there were birders out there who shared this information on list-serves and in chat rooms, and on birding hotlines.  And I hoped that there were birders out there who would be willing to met me come to their yards, and work there.  So, I threw myself on the kindness of strangers and started asking around.  I put my name on every list I could find.  I asked friends to pass my email address around to their friends.  I walked into random nature shops and asked if I could leave my contact information on billboards.  I did everything I could think of to get information on where Evening Grosbeaks were, and who’s feeders they were visiting; and responses started coming in!  I have gotten a ton of information on where these birds show up.  I have also been shown amazing hospitality by birders.  After figuring out where the birds were, I asked to go one step further.  I was hoping to be able to come to where the birds already were, and that meant visiting with birders who were willing to let me visit.  I have had the incredibly good fortune to find birders in three states who were willing to open their doors to me and my wife and let us come and spend some time in their backyards as I studied the birds there.  Some have let us camp in their back yards, others have given us a hot meal on a cold day, a few have even wanted to lend a hand with my work!  The kindness of strangers has been incredibly kind, indeed.

Even beyond their generosity, these birders have reminded me of how much value birders can be to ornithologists.  My master’s thesis would not have been possible without birders who were willing to help me out, and I will be continuing to rely on their generosity, and the generosity of others, as I pursue my Ph.D.  I would strongly suggest that other ornithologists think about ways of tapping into this amazing network of information and wonderful people, and I would also ask birders to think about letting a scientist into your yards.  By doing as simple a thing as putting up a bird feeder, anyone can make a big contribution to the study of birds, and want to thank all those who do.

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Subspecies are a fundamentally important unit of taxonomy.  They represent the diversity of adaptations that various groups can acquire as they respond their local environment.  In circumstances where barriers are long-lasting, they can represent the first steps in speciation.  When barriers are less permanent, they can tell us about the dynamics of how major features of a landscape can change through time.  Subspecies can also offer information in areas of mate choice and sexual selection, breeding behaviors, dispersal and gene flow, colonization events, and phenotypic plasticity.  With so much to offer, subspecies warrant a great deal of attention from biologists from a wide range of disciplines.

From a conservation point of view, protecting subspecies ensures that a wide range of the genetic, morphological, and behavioral variation within a species is preserved.  This leads to the preservation of the greatest possible adaptive potential for the species as a whole.  From a policy perspective, subspecies that are declining are protected by law under the endangered species act of 1973.  Therefore, proper identification is needed for decisions on listing and delisting designations and for the assignment of money and labor that result from such decisions.  From an evolutionary biology standpoint, subspecies can represent the transitory step of one species becoming many.  The process of observing and mapping such speciation events is one of the primary goals of evolutionary and population biology.

However, despite the importance and need for accuracy in subspecies designations there is little agreement or consistency with regard to how it is done.  Some of these inconsistencies arise from problems of definition.  Defining a species is a tricky task with different situations lending themselves to different criteria.  The biological species concept, the morphological species concept, the phylogenetic species concept and the rest all have their supporters, and each species definition leads to a different subspecies definition.

The biological species concept states that a species is a group of individuals that can breed and produce viable offspring with other members of the group, but not with individuals from outside the group.   This is the most widely used and accepted species definition in raptor biology.  The major difficulty with applying this definition to subspecies (a subspecies is a group of individuals which can breed and produce viable offspring with any other member of the group, but not with individuals from outside the group, but who usually breed with only a subset of the group) is that it is not easy, and sometime impossible, to trace movement and breeding patterns among different populations.  The morphological species concept is the oldest form of classification.  It states that a species is a group of individuals that all share a suite of physical characteristics with each other, but not with individuals from outside the group.  This concept is not well supported in modern biology; however it is the most frequently used as the method for designating subspecies.  The phylogenetic species concept states that a species is comprised of all of the descendants of a single common ancestor.  This idea is gaining strength as genetic techniques to determine descent become easier, faster, and cheaper.  However, this species concept does not have specific levels of separation that mark species and subspecies, so any such designations become much more subjective.

These different definitions lead to many problems.  Each of these definitions has areas of grey where disagreements can, and do, arise.  How much interbreeding is enough to consider two groups part of the same subspecies?  Which morphological characteristics are included in the diagnostic suite, and how different do they have to be?  How much genetic divergence is enough to warrant species or subspecies designation?  These are the questions that need to be settled when designating and naming subspecies.

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On the 8th of March, 2012, I saw my first Swainson’s Hawk of the year!  I always look forward to when these birds return to central California.  This bird was calling from a perch at the top of a redwood tree on campus.  It is a spot that seems to be favored by Swainson’s Hawks, as last year a pair set up a territory and nested in the same group of trees.  I wonder if this is one of the same birds.  Now, about a week after that first bird arrived, Swainson’s Hawks fill the skies over Davis as the bulk of the returning population begin to arrive.

Swainson’s Hawks undertake one of the longest migratory routes of any raptor in North America.  They leave from the plains of the continental USA and southern Canada in the early northern hemisphere fall and fly to Argentina.  There, they spend the southern hemisphere summer eating mostly insects.  Interestingly, not all the Swainson’s Hawks go on this long migration.  The birds that breed in California, which is a population that is somewhat separate from the rest of the species, have been found to generally only go as far as Baja California, Mexico.  What makes this group stop so much sooner than the birds that breed in the great plains?  Do any birds from the California population go to Argentina?  Do any birds from the great plains stop in Baja?  I don’t think anyone knows the answers to these questions, but they would be awfully cool to find out!

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