Why are the nighthawks where they are now?

I toyed with different versions of this awkward blog entry title, but really it ties into my previous post, “Where are the nighthawks now?”

As we saw in that post, birds can cover a lot of ground in a year.  Each of these places has to be habitat-friendly for a migrating bird.  Here in South Dakota, birds encounter a number of biome types, called ecoregions.

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I study Common Nighthawks in 47d, 46n, 42f and 47a.

 

47d – Missouri Alluvial Plain – Elevation 1100 – 1200 ft.

The human development of the Missouri Alluvial Plain over the last two centuries has separated the Missouri River from its floodplain.  A system of dams, levees, and stream channelization has largely controlled the flood cycles to allow intensive agriculture in the river bottomland.  Much of the northern floodplain forest has been cut, and oxbow lakes and wetlands have been drained to reclaim additional agricultural land.

46n – James River Lowland – Elevation 1200 – 1850 ft.

The boundary between the James River Lowland and the Drift Plains (46i) to the north represents a broad phenological and climatic transition zone.  This ecoregion is characterized by mesic soils, warmer temperatures, and a longer growing season than the Drift Plains (46i).  These differences are reflected in the crop types of the region.  Winter wheat, corn, and soybeans are more prevalent in this ecoregion’s milder climate.

42f – Southern Missouri Coteau Slope – Elevation 1400 – 2200 ft.

The Southern Missouri Coteau Slope differs from the Missouri Coteau Slope (42c) to the north; it has mesic soils rather than frigid soils and a substantial cap of rock-free loess.  To the south, the coteau areas east of the Coteau Slope ecoregions (42c, 42f) become progressively narrower and more eroded.  The level to rolling uplands of the Southern Missouri Coteau Slope are planted in sunflowers, wheat, millet, and barley.  Corn is a marginal crop that does well in wet years.  The stream drainages tend to be grazed.  Willows, green ash, and elm grow in the riparian areas.

47a – Loess Prairies – Elevation 1200 – 1700 ft.

The Loess Prairies of Iowa and South Dakota surround the perimeter of the Des Moines lobe of the Late Wisconsinan glaciation.  Of the two areas in South Dakota, the northern one is distinguished from neighboring regions by its rock-free soil and a paucity of wetlands.  The southern area is more highly dissected, with deciduous woodland and brush on the steeper slopes and in the draws.

(Source: sdakotabirds.com, EPA)

These four ecoregions even within southeastern South Dakota vary quite a bit, and so do Common Nighthawk abundances. The change in landscape and nighthawk abundance are even more marked when you move further west into the Badlands, western grasslands, and the Black Hills where row crop dominance drops away.

Common Nighthawks need gravel rooftops or gravelly parts of grassland and rangelands with shortgrass prairie or heavily grazed tallgrass.  Or, they can thrive in open forests, like those of the Black Hills. Below is a map for all years, all months for the ebird Common Nighthawks sightings in South Dakota.  You can see a concentration of nighthawks in the west in the Black Hills and Badlands and in urban areas like Vermillion and Sioux Falls.  Of course, these sightings have some bias as to where observers tend to be.

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Common Nighthawk sightings in South Dakota (source: ebird)

Migrating flocks can show up anywhere because they don’t need gravel areas for camouflaging eggs.  My first sighting of nighthawks in South Dakota was in September, 2011, the year before I moved here.  It was an unlikely spot to see them.  There was a a group of 100 flying over row crop along I-90.  Of course, migrating nighthawks have the benefit of covering a lot of ground in a day and can forage while flying.  Their needs are more simple than a migrant seed eater that needs a forest, as my lab mate Dr. Ming Liu found.

It’s also important for researchers to understand habitat use in the other areas of a bird’s yearly migration.  Cornell Lab of Ornithology’s Golondrinas de las Americas foundation and other organizations supply grants to researchers in South America and Central America.  Last year’s North America Ornithological Conference featured symposia of South America and Central America research.

Newer technologies are helping researchers  throughout an organism’s range with more expansive data.  Satellite tags, like those developed for the Argos system,  are becoming smaller and lighter which enables research of larger array of species.  These data can be downloaded without recapturing the bird, which is crucial for wily birds like Common Nighthawks.

Behold, the future!

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Source: Futurama

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Sdakotabirds.com source:

Ecoregion summaries from “Ecoregions of North and South Dakota”, U.S. EPA published map. Primary authors: Sandra A. Bryce (Dynamac Corporation), James M. Omernik (USEPA), David E. Pater (Dynamac Corporation), Michael Ulmer (USDA), Jerome Schaar (NRCS), Jerry Freeouf (USFS), Rex Johnson (SDSU), Pat Kuck (DENR/NRCS Liason), and Sandra Azevedo (OAO Corporation).

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Where are the nighthawks now?

The short answer?  They are on their way back to North America.

Cornell Lab of Ornithology’s ebird web site has interactive maps where you can enter your birding data and view others’. You can enter queries for any year since 1900 (they’ve plugged old data into the system) for any species anywhere in the world.  Very cool, huh?

When there are few observations, you can see individual blue markers.  When there are many, the observations show up as pixels of varying degrees of purple. Below are the nighthawk maps for all years, by month.

Here are the nighthawks now in March.  They are coming!

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Common Nighthawk observations in March (Source: ebird)

By May, they are well into the U.S.

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By July, they are well into Canada. Some stay and breed in Central and South America.

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In October, they are making their way back to their wintering grounds in Central and South America.

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By January, they have settled into their wintering grounds in Central and South America and Florida.  But in a couple months, they will start making their way back.  No rest for the wicked.

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Common Nighthawk observations in January (Source: ebird)

Halloween Outreach

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My nighthawk wings

There is something deeply nerdy about dressing up as your research subject for Halloween.  Last fall, I made the nighthawk wings pictured here.  I had a lot of card stock from my landscape art and thought I would make some wings.  I bought some black angel wings from Walmart, and pulled the feathers off all but the central harness so that I could glue on longer cardboard pieces using Gorilla wood glue.  I then consulted a diagram of a bird wing for the feather types.  For the primary/secondary feathers (which come together when the wing is folded like this), seen here at the bottom of the wing, I cut long strips of black construction paper and made tiny cuts along the edges to give them the feathery texture and glued strips of white to each feather.  I then glued the primaries/secondary feathers down.  Then I cut out identical pieces of black and brown for the primary/secondary coverts, seen here in the middle, and glued those down.  I repeated the primary/secondary coverts for the wing coverts, seen here at the top.

It’s a simplified version of a wing with fewer feathers than nighthawks actually have.  But, it can be made very quickly if you make three templates: 1) the primary/secondary feather, 2) white wing bar, and the 3) covert. 

I wore it to the Vermillion Area Farmers Market Halloween celebration where kids came to trick or treat.  I sold my shadow boxes to benefit nighthawk research and handed out candy.  In case folks were wondering what a nighthawk was, I thought this would be fun.  The kids seemed to like the wings.

 

Pronghorn Phylogeny

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The Pronghorn (Antilocapra americana) is my favorite North American ungulate.  Not only is it the fastest land mammal in North America, and the second fastest land mammal worldwide, but it possibly evolved to outrun a North American cheetah-like cat 10,000 years go in the late Pleistocene.

More interestingly, recent genetic research nominates a surprising candidate as the closest living relative of the pronghorn.

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Pronghorn male (Source: Tom Bean/NPS.gov)

Was it  a deer?

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Mule Deer (Source: NPS.gov)

Some deer share  similar markings with the Pronghorn, but that’s pretty superficial. Not only that, Pronghorn have a bony permanent plate within their horns unlike deer which shed their entire antlers every year. Deer comprise the Cervidae family.

Plus, Pronghorn ancestors diverged from their closest relative in  the early Miocene (23.03 to 5.3 million years ago) before the continents drifted and Africa and North America were still attached. I think we can expand our search.

What about Old World antelopes?  That’s what we call them, right?  Pronghorn antelopes?  In fact, if we do a google search of “antelope family”, the first result is the Pronghorn. The internet is always right. Right?

Old World antelopes are part of the Bovidae family which include cattle, buffaloes, bison, goats, gazelles, goats, yaks and sheep.

Here’s an antelope that looks like a Pronghorn, the Springbok.

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Springbok (Source: eol.org)

Yeah, but this is also a member of the Bovidae family:

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Himalyan (Source: eol.org)

So much for markings.  Ah, the perils of gross morphology in building phylogenies.  Basically, we can attribute many false assumptions about relatedness between organisms just on coat markings and other superficial observations.

Besides, Bovidae have hollow horns.  This isn’t quite what Pronghorns have.

Hey, here’s a crazy idea.  What about Giraffes?  They also have a bony protuberance beneath their horns.

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Pronghorn skull (Source: University of Oregon Museum of Natural and Cultural History)

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Giraffe skull (Source: University of Edinburgh)

Skull formation as a method of differentiating relatedness between organisms seems superior to coat markings, but it’s still gross morphology.  Ultimately, DNA evidence shows the Pronghorn family Antilocapridae are most closely related to the Giraffe family, Giraffidae, which also includes Okapi and Zebra Giraffe.

That means Pronghorns and Giraffes shared a relative back when the continents were conjoined.  Then, when the continents drifted, they became separate lineages. That’s very cool.