Hubbard Fellowship Post – Mixed-Up Flickers

This post is written by Olivia Schouten, one of our Hubbard Conservation Fellows.  Olivia hails from Pella, Iowa, and has strong experience in prairie ecology.  Look for more posts from her, as well as our other Fellow, Alex Brechbill, in coming months.

One of my favorite things about the change from winter to spring is the return of migratory birds. While the rest of spring has been reluctant to arrive, I am still reminded of the inevitable change in season as more and more birds arrive in the area. What started with sandhill cranes back in February just continues as killdeer, turkey vultures, and swallows, among others, seem to appear overnight when a favorable wind blows from the south.

Among the new arrivals are northern flickers, a woodpecker that despite its name, tends to feed on the ground. This migratory bird arrived here on the Platte River quite suddenly over Easter weekend, and they’ve been everywhere ever since! While common across North America, if you’ve spent any time travelling and recognize this bird, you may have noticed something interesting: birds in the eastern half of the continent are not the same color as those in the west.

In fact, there are two color variants of northern flickers. Eastern birds are called yellow-shafted flickers, and those in the west are red-shafted. The ‘yellow/red-shafted’ designation refers to the unusual coloration on the shafts of the wing and tail feathers of this bird. Where most birds’ feathers either have white, brown, or black shafts, northern flickers’ are bright yellow or salmon-red, depending on the variant. The undersides of these feathers also display the same color, resulting in bright flashes of color when the birds fly, turning a somewhat drab bird into something spectacular.

There are some other differences between the eastern and western variants. Yellow-shafted birds have a red crescent on the nape of their neck, and while all males have a ‘mustache’ patch of feathers extending down their cheek, it is black in yellow-shafted males, and red in red-shafted males. These differences are so clear, that for many years the two variants were considered different species.

This red-shafted flicker displays the red mustache sported by the males of this species.  Photo by Chris Helzer
In contrast, yellow-shafted northern flickers have a red crescent at the nape of their neck, and the male’s mustache is black. All flickers have a bold black crescent across their chest. Photo by Olivia Schouten
Though overall drab in appearance, northern flickers flash bright yellow or red when in flight. This yellow-shafted male followed around the female at the left of the photo for several minutes. Notice the female is missing the mustache of the males. Photo by Olivia Schouten

However, what complicated that classification was the presence of hybrids of the two variants in a large zone stretching from Texas to Alaska, cutting right through the heart of the Great Plains, including central Nebraska. These hybrids, called intergrades, display combinations of facial traits found in the red- and yellow-shafted variants. In my home state of Iowa all you will see are yellow-shafted flickers. However, here in Nebraska I see flickers with their wings flashing everything from yellow to dark salmon red, and all colors in between.

Though I couldn’t get a clear picture of this bird in flight, it is still clear that the wings of this bird grade from yellow to orange. While the facial markings of this flicker suggest it is a yellow-shafted variant, the coloration of the wings point to it being an intergrade, the result of the hybridization of a yellow-shafted and red-shafted variant. Photo by Olivia Schouten

Now considered one species, northern flickers are just one example of a common trend seen among North American birds. If you flip through a bird field guide and study the range maps, you will often find pairs of similar species where one occurs in the east, and one in the west, with the transition between the two occurring right down the middle of the continent. Eastern screech-owls and western screech-owls, ruby-throated hummingbirds and black-chinned hummingbirds, eastern and western wood-pewees, eastern and western meadowlarks, vireos, bluebirds, warblers, and on and on and on, you can’t escape the pattern. For many, it’s as if there was an invisible wall through Oklahoma, Nebraska, South Dakota, and upward keeping these species from spreading any further.

Clearly, something is going on in the middle of the continent when it comes to birds, and this hybridization sometimes makes it difficult for ornithologists to determine where species begin and end, or whether they should even be considered different species at all. One of the leading hypotheses is that climactic changes during past ice ages created unsuitable habitat in the center of the continent that separated previously connected populations. Time allowed for the divergence of these now separate populations, and when they reconnected as the ice retreated, enough differences had accumulated that they were no longer the same species.

Of course, this divergence was carried to varying degrees of completion depending on the bird. While some of these species pairs, like flickers, hybridize quite readily, and in fact never quite diverged enough to be different species at all, others, such as meadowlarks, while nearly identical in appearance, developed different enough songs that their separation was maintained.

So pay attention to the flickers around you here in Nebraska and elsewhere along the hybrid zone, and see if you have can spot the different variants!

Though I’m not entirely sure what is happening in this photo, I believe the male flicker here was displaying its tail to the female in some sort of courtship behavior. Whatever it was doing, it made for a nice demonstration of the brightly colored feathers tucked away by this otherwise unassuming bird. Photo by Olivia Schouten

Report from 2011 Grassland Restoration Network – Part 1: Herpetology

 

Last week was the annual workshop of the Grassland Restoration Network.  This year, the host was The Nature Conservancy’s Kankakee Sands Prairie/Wetland Restoration Project in Indiana.    There were more than 80 people – mainly from Illinois and Indiana this year.  As always, the workshop was an opportunity for sharing notes and ideas on prairie restoration, but we also had a particular focus on animal habitat this year.

I felt like the workshop was especially productive and interesting this year, and have several posts worth of information to share from it, but I thought I would start with herpetology.  Kankakee Sands is restoring wetland habitat by plugging/filling ditches and also doing some excavation – and then seeding wetland vegetation.  One of the goals of that work is to create habitat for reptiles and amphibians. 

Dr. Bob Brodman, from nearby St. Joseph’s College, has been sampling amphibians (and reptiles) in the area since before restoration work began, and has observed exponential increases in populations at the restoration site.  It’s not really surprising that he’s found higher numbers of amphibian populations, since the Conservancy has added new wetlands to the site.  More interesting – and gratifying – is that he’s also finding that the number of amphibian species per wetland is also increasing (as is the total number of amphibian species across the site).  In addition, Dr. Brodman has collected data on other amphibians and reptiles that seem to show those species moving in from nearby remnant habitats.  Since the major goal of the Kankakee Sands project is to reconnect those disjunct remnant habitats (for vertebrates, invertebrates, and plants) those data are encouraging.

Dr. Bob Brodman (herpetologist) examines and photographs a toad.

Restoration ecologist Ted Anchor led field trips for this year’s network participants to show the immediate colonization of newly-created wetlands.  We looked at two wetlands – one with muck soils and one with almost pure sandy soils.  At both wetlands, we saw numerous frogs and toads, though they were much easier to see (and catch) at the more sparsely-vegetated sandy site.  Additionally, we were finding both Fowler’s toads and American toads, as well as many that appeared to be hybrids between the two species.  Dr. Brodman hypothesized that the temperature and moisture conditions this spring had led to the two populations breeding simultaneously in ponds where they would normally show up a couple of weeks apart.

Ted Anchor showing off the muck soils at one of the wetlands on the field trip. The muck had prevented the immediate area from being farmed, and also created a quick establishment of plants from the seed bank - and from seeding - after excavation was complete.

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One of many toads that had physical characteristics of both Fowler's and American toads.

Ted and Dr. Brodman both discussed some of the important factors to consider when restoring wetland habitat for frogs and toads.  In general, they said that most amphibians utilize a buffer zone of upland habitat (about 200 meters wide) around the actual wetland habitat itself.  While that habitat is very important, the most critical factor for annual breeding success tends to be the length of time water is present in wetlands each spring/summer because that determines whether breeding occurs and whether tadpoles can successfully mature before their ponds dry up.  Water depth and organic matter in the wetlands soils can both affect the length of time that water stays around. 

Creating wetlands with varying depths, including at least a few places where it is nearly permanent can help ensure breeding success (though fish and bullfrog populations can be counter-productive, so that can be a tricky line to walk).  Most wetland restorations at Kankakee Sands have very sandy bottoms – as do the ones we’ve done along the Platte River in Nebraska.  Those sites tend to hold water for shorter times than do sites with more organic matter (or clay).  That organic matter will accumulate over time, gradually helping to increase breeding success over time, but again, creating some deeper pools can help in the meantime. 

In addition to helping hold water, organic matter may have two other benefits.  First, the darker colored soil may improve the effectiveness of the dark-colored tadpoles’ camouflage – and could increase survival (logical speculation from Dr. Brodman).   Second, the organic matter increases the density of vegetation, which may help amphibians better thermoregulate and conserve moisture under the shade of those plants.  Those plants probably provide more and better hiding places too…

Ted Anchor and network participants at the sandier of the two wetlands visited on the herpetology field trip. You can see the sparse vegetation in the sandy soils.

At our Platte River Prairies, we’ve experimented with trying to supplement organic matter levels in our restored wetlands by “top-dressing” excavated wetland bottoms (spreading top soil on them).  While it likely increases organic matter, the main impact we’ve seen so far is an increase in invasive plants – and/or lower plant diversity.  It may be that waiting for those wetlands to accumulate organic matter slowly will allow a more diverse plant community to take hold – but may mean lower breeding success for amphibians and other species in the meantime. 

A final discussion topic during our wetland field trips centered on habitat structure for shorebirds – as well as amphibians and other species – as restored wetlands mature over time.  Obviously, the bare sand (or sparse vegetation) conditions immediately after wetland construction provide great habitat for shorebirds.  As that plant community develops over time, a few dominant plant species often end up covering much of the area, reducing bare ground, decreasing plant diversity and somewhat simplifying habitat structure.  We had an interesting set up discussions about whether (or how often) it was valuable to periodically “reset” those early conditions through intensive disturbances such as grazing or disking – and there was no consensus among the group. 

We’ve experimented with periodic intensive grazing at our Platte River sites to create bare ground in and around the deeper portions of our restored wetlands.  Within a year or two after the cattle have moved to another location, those wetland plant communities recover their former plant composition and habitat structure.  We’ve found that kind of grazing to be useful in preventing species like cattails from choking out open water habitat – and in creating temporary habitat for shorebirds and other species that like bare ground.  On the other hand, there are certainly impacts from the cattle in terms of nutrient inputs and sedimentation.  I don’t have the answers about how to balance those tradeoffs.  At this point, we’re banking on the ability of our sites to absorb the potential negative impacts – on a short term periodic basis – and we appreciate the apparent benefits.

It was great to have the opportunity to see what the Conservancy’s 6,000 acres of restored grassland/wetland habitat is doing for reptiles and amphibians in Indiana last week.  As I’ve mentioned before, I find it valuable to think about my own restoration work through the eyes of various animal and plant species.  I admit that toads aren’t one of the species I consider very frequently, so it was helpful to be reminded of the importance of those species and the types of conditions they require.  As I walk our sites this week, I’ll be looking at our wetlands with a different perspective than I would have last week.