A studio for bird study

Category: Uncategorized

Thoughts on the Past, Present, and Future of the Snowy Plover in North America

by Bryce W. Robinson

Snowy Plover - Charadrius nivosus. 11 x 14 " prismacolor on bristol

Snowy Plover – Charadrius nivosus. 11 x 14 ” prismacolor on bristol. Image copyright Bryce W. Robinson 2015

I’m becoming increasingly fascinated with how our changing world may impact the distribution of a given species, either shifting or fragmenting breeding ranges. I have a particular affinity for the family Charadridae , and I’ve found myself paying closer attention to one species in particular, the Snowy Plover – Charadrius nivosus. The Snowy plover occupies a widespread but disjunct breeding range in its western North American population(Figure 1). This range is likely a result of the bird’s need for specific (in turn limited) habitat for breeding.

Figure 1. Range of Snowy Plover - Charadrius nivosus in North and Central America. Image taken from Birds of North America Online (see referenced information)

Figure 1. Range of Snowy Plover – Charadrius nivosus in North and Central America. Image taken from Birds of North America Online (see referenced information)

The Snowy Plover is a species that has faced many challenges with the ever increasing human presence. Throughout the bird’s North American breeding range (Figure 1), human impacts have caused a multitude of threats to its ability to reproduce. These threats include but are not limited to environmental contaminants, an increase in nest predators such as Raccoon, Common Raven, Coyote, and Red Fox, all of which have experienced a human-subsidized boost in population numbers in recent decades, and recreation on beaches causing both disturbance and nest destruction. A great discussion of all factors impacting Snowy Plover populations can be found on the Birds of North America species account under the Conservation and Management section.

Multiple organizations are working with state and federal wildlife authorities to augment the negative impacts humanity and its residuals are having on Snowy Plover populations. These organizations include Point Blue Conservation ScienceFriends of the Dunes, the National Audubon Society, and many others. The effort is impressive and has seen some success. Still, there is a looming threat on the horizon, the impacts of human induced climatic changes.

What the threats of climate change mean for the Snowy Plover in western North America and across the rest of its range in S. America are still to be determined, but I’d like to emphasize the need to determine and augment these threats as they are occurring. I’ve become aware of a population level analysis that is meant to track the distributional patterns of a given species throughout its yearly cycle (Ruegg et al. 2014). The idea is to identify population structures during the major life events of a species through genetic analysis of individuals at each location; breeding, migration, and non-breeding. Understanding where individuals spend each part of the year holds the power of  identifying where negative impacts are occurring that are driving population declines. This is the big idea behind the banding effort, but this technique provides larger sample size and more power for determining population structures. It’s a huge step in the right direction.

My point is, wouldn’t this be a great tool for assessing changes in populations of the Snowy Plover over its disjunct range as the impacts of climate change become more visible and severe? The answer is yes, and we ought to begin the effort…

Referenced Information:

Page, Gary W., Lynne E. Stenzel, G. W. Page, J. S. Warriner, J. C. Warriner and P. W. Paton. 2009. Snowy Plover (Charadrius nivosus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/154

Accessed 7 February 2015

Ruegg, K. C., E. C. Anderson, K. L. Paxton, V. Apkenas, S. Lao, R. B. Siegel, D. F. Desante, F. Moore, T. B. Smith. 2014. Mapping migration in a songbird using high-resolution genetic markers. Molecular Ecology 23:5726-5739

Barred Owl – Out of Range but Seemingly Comfortable

by Bryce W. Robinson

 

Around the turn of the year a Barred Owl – Strix varia, was reported in Boise, Idaho. The owl has been seen regularly for the past month. Barred Owls occur in Boise once every few years as vagrants from somewhere unknown. This Barred Owl showed up in a city park on the east side of town, only about a mile from the foothills. The peculiar part is that the park is adjacent to the Boise River, a large wooded area, and acres of open field. Instead of occupying these more wild, less human areas, the owl has chosen the back yards adjacent to the park to roost. The bird hunts the park edges and greens at night, apparently having loads of success. This behavior is a testament to the hardness of this species against human disturbance. It is one of those few species that seems to do well with the world we are creating.

I took the video above a few days ago just before sunset. The owl was alert, no longer snoozing. The most interesting thing about the video is the birds behavior coupled with the anthropogenic noise. In the clip you can hear a man playing fetch with his dog, someone closing a house door, and many other human sounds typical of urban living.

Why is this Barred Owl able to tolerate a lifestyle like this, yet other species are so sensitive to disturbance? The Barred Owl’s closest North American relative, the Spotted Owl, is certainly having a hard time with the way we are changing its world. These types of questions are worth entertaining as more and more we change the world around us, better for some but certainly not for all.

 

Learning New Skills – Preparing Study Skins

by Bryce W. Robinson

From left to right: Sora - Porzana carolina, 2 male Brown-headed Cowbirds - Molothrus ater, 2 female Brown-headed Cowbirds - Molothrus ater

From left to right: Sora – Porzana carolina, 2 male Brown-headed Cowbirds – Molothrus ater, 2 female Brown-headed Cowbirds – Molothrus ater, all drying after preparation.

I’ve embarked on a new adventure in my ornithological education. I am now learning how to prepare study skins for museum collections with the help of my advisor Dr. David Anderson. My personal catalogue number 001 is a female Brown-headed Cowbird – Molothrus ater (farthest right specimen in the photo).

This is a new experience for me, and one that I’ve been looking forward to for a very long time. I’ll be sharing what I learn along the way.

Baltimore Oriole – Icterus galbula

by Bryce W. Robinson

Baltimore Oriole 9 X 11" Prismacolor illustration on bristol. Image copyright Bryce W. Robinson

Baltimore Oriole 9 X 11″ Prismacolor illustration on bristol. Image copyright Bryce W. Robinson

I recently illustrated the above Baltimore Oriole for someone. I’ve mentioned earlier that I’d like to supplement the exercise of my illustrations with reading and reporting on an academic article relating to my subject. I chose an article that is a bit dated (Rohwer and Johnson 1992), but it peaked my interest as it discussed differences in timing of molt between the two subspecies of the then Northern Oriole. Now we understand that the Northern Oriole is comprised of two species, the Baltimore Oriole (pictured) in the east, and the Bullock’s Oriole of the west.

I learned from reading the paper that the two species differ in the timing of their pre-basic molts. Bullock’s Orioles begin their pre-basic molt after fall migration whereas Baltimore Orioles begin their pre-basic molt before and molt during migration south. The paper then suggests that the difference is under genetic control. Rohwer and Manning (1990) found a female “hybrid” (in 1990 it would be considered an intergrade) in fall undergoing a second pre-basic molt. This suggested that the bird had molted before its migration south and was undergoing a second molt at that time. This was thought to be a result of the confused genetic control of molt timing for both species, as it molted on its breeding grounds as Baltimore Orioles do, and was again molting after migration as Bullock’s do.

The interesting aspect of this article is that it discusses the differences in molt timing and attributes this difference to a genetically controlled mechanism. This supports the genetic difference between the two birds, and is likely an article used for support when the decision came to split the Northern Oriole into what we now understand as two species today, the Baltimore and Bullock’s Oriole.

I really enjoy looking through the vast scientific literature of the ornithological world. I quickly find something that interests me, and always come away with some degree of enlightenment following each read. Pairing illustration with reading is absolutely a worthy exercise that I will continue.

Referenced Literature:

Rohwer S. and J. Manning. 1990. Differences in timing and number of molts for Baltimore and Bullock’s Orioles: Implications to hybrid fitness and theories of delayed plumage maturation. Condor 92: 125-140

Rohwer S. and M. S. Johnson. 1992. Scheduling differences of molt and migration for Baltimore and Bullock’s Orioles persist in a Common Environment. Condor 94: 992-994