100 Years of the Migratory Bird Act

This year marks 100 years since the passage of the Migratory Birds Treaty Act, one of the earliest pieces of conservation legislation passed by the US Government. This law made it illegal to kill native birds or remove or disturb their nest and eggs. (16 US Code Section 704 subsection A) This act served to protect many endangered species of birds which were under threat from over hunting like waterfowl whose feathers were highly prized. This act has seen many successes and has helped replenish and protect many bird species like the Snowy Egret and other waterfowl.

On side effect of this law was that egg collecting became an illegal hobby. While this act was extremely good protecting birds, it also means most of the eggs we have in Museum collections are now a 100 years old. Bird eggs can be valuable sources of data regarding pollution and environmental damages, and this data can be invaluable in crafting governmental responses to these threats. In a very real sense birds are, for the lack of a better phrase, a canary in the coal mine. For example the impact that DDT and similar pesticides were having on bird eggs were noticed far earlier than its impacts were seen or felt on humans, as illustrated in the work of Rachel Carson in Silent Spring. As such bird eggs can serve as a vital tool for scientists when considering the impact of contaminants in the ecosystem and their potential impacts on human life.

The Migratory Bird Treaties Act has presented a challenge and an opportunity for scientists interested in studying birds for contaminants. The challenge is that because much of the avian life in the United States is composed of native bird species, which are protected under the Migratory Bird Treaties Act, scientists cannot easily collect bird eggs from these birds. However, nnon-native birds, such as the House Sparrows, are exempt from the law. House Sparrows are native to western Eurasia and Northern Africa. these birds were introduced to NY in the 1800’s and have since spread across the US. There non-native status allows Sparrow Swap to revive the egg collecting so that House Sparrow eggs can be used to research pollutants, and more importantly in terms of helping conserve native species, swapping out the eggs allows us to study a method for controlling this invasive species.

However, because only house sparrow eggs and a handful of other species are legal to collect makes it very important that the eggs collected are indeed House Sparrow eggs. The color, speckling, and shape of an egg can change a lot not only between species, but also within a single species. This can make it hard sometimes to confirm just by looking at an egg, what species it is from. Where the nest is (in a cavity or in a tree), what the nest is made of (pine needles or moss), the structure of the nest (neat or messy) and if you see an adult bird fly in and out of the nest are all important clues that can confirm the identity of the eggs. For example, House Sparrow nests are made of coarse dried vegetation, often stuffed into the hole until it’s nearly filled. The birds then use finer material, including feathers, string, and paper, for the lining.

Below are a few examples of other species with similar eggs to house sparrows:

House Sparrow Eggs. Photo from Sialis.org


Cowbirds are indigenous birds which will sometimes parasitize a sparrows nest by laying an egg in the nest. As such they are protected by the Migratory Bird Treaties act and their eggs cannot be removed from a nest without permission from your States wildlife management agency. Please remember that while the two eggs look similar, that one is a house sparrows egg, and one is a cowbirds. An easy way to tell the difference is to look at the size (if they are in the same nest) and the degree to which the eggs are round. The larger and more round one of these eggs are the more likely they are cowbird eggs. In addition if there are other intact eggs of another bird species in the nest or adult birds brooding, it is likely that the eggs are cowbird eggs unless the brooding birds are House Sparrows.

Cowbird egg in a bluebird nest. Photo from Nestwatch.

Tufted Titmouse
Tufted titmouse eggs and those are also protected species and you can tell the difference between the two since House Sparrow eggs are generally glossier and a bit longer on average than a Tufted Titmouse egg. Titmice build cup-shaped nests inside the nest cavity using damp leaves, moss and grasses, and bark strips. They line this cup with soft materials such as hair, fur, wool, and cotton, sometimes plucking hairs directly from living mammals.

Tufted Titmouse Eggs. From Sialis.org

House Finch
We have also received House Finch eggs, these birds are also protected species. Compared to a House Sparrow the Eggs of a House Finch are smaller, lighter colored, generally less speckled, and the speckles are generally black to purple in color. A House Finch’s nest is a cup made of fine stems, leaves, rootlets, thin twigs, string, wool, and feathers, with similar, but finer materials for the lining. This what House Finch Eggs look like.

House Finch Eggs. Photo from Nestwatch.

We hope this helps if you come across an unusual egg! Don’t hesitate to contact us hear at Sparrow Swap if you have any questions.

This post was written by Rohan Krishnamoorthy. To learn more about Rohan and the rest of the Sparrow Swap Team, check out our Team Page.

Double Yolker!

In order to test the eggs for contaminants, we first have to separate the egg contents from the eggshell. To do this we use a dremel tool to carefully cut through the eggshell, but not the membrane. We then lift up the piece of cut eggshell. Here, there is always a moment of hesitation: what will be inside?

Sometimes we find a nice yellow yolk with a viscus albumen (the whites). However, as the eggs age, both the yolk and albumen start to break down making them runny. On other instances we find more developed embryos, and to be honest, the scene can be quite gruesome.

The worst, by far, is a rotten egg. Sometimes just with the slightest touch of the dremel, the egg will explode sending shell and contents everywhere. For example, one of our middle school interns picked a piece of shell out of my hair.

But occasionally, we will find something surprising. Like a double yolker! While taking photos of the clutch, Aubrey noticed that one egg was bigger than the others in the clutch (Egg C).

When we went to curate it, we found not one, but two perfect yolks.
I’m not sure anyone has ever looked at the odds for house sparrows, but for chickens the odds of getting a double yolker is about 1 in 1,000. Just as in humans, twin birds can be fraternal or paternal. If a female produces two yolks in a short enough time span (about three hours), than both yolks will travel through the oviduct together as one egg creating fraternal twins. If the embryo splits within the egg during development than the twins will be paternal. Most of these twins will die in the egg completing for the same resources. However, there are some cases where twin egg are able to successfully hatch!

One of these cases happens to be in bluebirds! Back in 2013, a Nestwatch volunteer in State College Pennsylvania found more nestlings in a nest of bluebird than there had been eggs! Twins had successfully hatched! These rare occurrences can only be documented through having vigilant and dedicated nestbox monitors and naturalists around the world.

This post was written by Suzanne Hartley, to learn more about Suzanne and the rest of the team check out the Sparrow Swap Team page.

A day in the life of a Sparrow Swap intern.

Hi all! My name is Heather Colter and I intern at the biodiversity lab in North Carolina Museum of Natural Sciences for Sparrow Swap! A little background info, I am going to be a senior in the fall at NC State University and my major is Fisheries, Wildlife, and Conservation Biology in the College of Natural Resources. I have really enjoyed my time with the Sparrow Swap team learning not only the technicalities of the project, but also getting to know the members and leaders within. Not to toot any horns, but the interns who work with Sparrow Swap are really important to the whole of the project; we work really hard to keep everything straight.

One of my favorite aspects of the project is when we go out into Raleigh and check the various boxes we have put out. It’s always such a treat when we find eggs, or, like in the photo above, when those eggs have hatched and become fresh baby birds! This photo was taken at the Farmer’s Market in Raleigh, it is a clutch of house wren chicks; the parents were nearby making a ruckus but it was a great find nonetheless! It was extra special because the six eggs we had counted in the previous week turned into six healthy and alive chicks, so that’s a great bonus.

Other duties for the interns include neverending data-entry/proofing, measurements of eggshell thickness, and curation of the clutches sent to us. Curation happens before we can get to measuring thickness; for curation we take the eggs and we measure their length and width and take a final mass to determine if there was any leakage or “weeping” since the egg first came to us and we took its initial weight. After that we use a Dremel tool to cut through the shell and then we poke through the membrane underneath with a instrument resembling a long metal toothpick. We then jar the contents of the egg if able to, and then we wash out the inside of the eggshell and leave it to dry and then we mark it with the clutch number and specific letter (A, B, C, D…) with an archival pen and store them until someone is ready to take their thickness measurements. Measuring the thickness is done with a tool called a micrometer, and we take six individual measurements of the sawed off cap of each egg within each clutch, or we use a broken piece of the eggshell if there isn’t a cap to measure. Of course, we write down all of these measurements into sheets, along with notes, and then we enter the information into the Sparrow Swap database. Working with Sparrow Swap has been an amazing opportunity and I have enjoyed it every step of the way!

This post was written by Heather Colter. To learn more about Heather and the rest of the Sparrow Swap Team, check out our Team Page.

A pest around the world

How did house sparrows become a pest? With the spread of agriculture and urbanization sparrows have become one of the abundant groups of birds in the world. Most sparrow species are closely linked with humans and spread with people as humans moved out of Africa and throughout the world. Perhaps the most successful sparrow, and the one we all know about, is the house sparrow, who can be found on every continent in the world save frigid Antarctica. Throughout time, as their abundance has fluctuated so has public opinion about these resilient little birds. Today we will look at the story of sparrows around the world, and how public perceptions and management has changed over time.


As humans moved out of Africa and into Europe, so did our sparrow friends. Being mostly seed eaters, sparrow ancestors were migratory. But the development of agriculture gave sparrows a consistent source of food year round. Like us, they settled, nesting in the buildings we built and eating the crops we produced. During the 1700’s there was an explosion in the European sparrow population as human settlements spread further and agriculture continued to focus on cereal grains such as wheat and oats, an ideal food source for sparrows.

By the mid 1700’s there was a superabundance of sparrows throughout Central Europe, with some written accounts describing flocks of sparrows so large that they blocked out the sun. These enormous flocks of sparrows could decimate important crop yields at a time when cereal grains made up a substantial portion of crops grown in Europe, making the sparrow a worthy foe. To combat this problem, many local governments established a bounty in which sparrow heads could be turned in to the government for tax credits. By the end of World War II, the first observable declines in the European sparrow population were seen. This change is likely due to a decrease in horse manure, more efficient grain harvesting technology, and poultry no longer being fed in the open. It is difficult to know whether the management strategies implemented by governments have led to a continued decline in house sparrow numbers or whether changes agricultural practices have played a bigger role. Ironically, in many European countries today house sparrows are now a protected species as their numbers have declined so much. There are now campaigns in the United Kingdom to save the house sparrow!

A house sparrow eating grain from a bird feeder. Photograph by Tammy McLean


One of the most interesting stories of sparrow control comes from China, during the reign of Mao Zedong and “The Great Leap Forward”. Mao considered the Eurasian tree sparrow (a close relative of the house sparrow) one of the “four great pests” to the nation because of their abundance and negative impact on grain crop yields. In March of 1958 Mao declared war on tree sparrows, and people all over the country went outside banging pots and pans together, waving flags, destroying nests, and killing nestlings with guns and slingshots.

At first, the effort appeared to be a remarkable success as crop yields initially improved. But before long, locust and grasshopper populations, freed from sparrow predation, exploded and decimated the grain crops. The crop damage from the insects lead to a famine in which more than 35 million Chinese people died. In a desperate attempt to stop the destruction, the government began importing sparrows from the Soviet Union. Following this disaster, Mao quickly protected tree sparrows and added bedbugs to his lest of four pests instead. This example illustrates the severe damage that can be inflicted when sweeping changes are made to an ecosystem.

Shen Nan (沈枬)
1959, February
Eliminating the last sparrow
This poster was meant for use in schools, and was part of a series. Sparrows were one of the Four Pests, together with flies, mosquitoes, and rats.


What can we learn from these failures in providing effective management of pest species? In both the European and Chinese stories, the problem came from a basic misunderstanding of how sparrows function in an ecosystem. Prior to the European sparrow population explosion of the 1700’s, written accounts show that some were already advocating for control of sparrows by destroying nests and eggs. But it wasn’t until the population exploded and started decimating crops that any action was taken. In China’s case, the government thought that tree sparrows strictly fed on seeds, and it wasn’t until after the sparrow population had been destroyed that they found research showing that tree sparrows also can control insect populations because they do feed on insects during breeding season.

The sparrows in China and Europe were a native species, but house sparrows were purposely introduced from Great Britain to the United States in the 1850’s as a form of pest control. 50 years after their introduction, house sparrows had spread virtually across the entire country and are almost universally regarded as pests. Instead of providing pest control, house sparrows are competing with our native bluebirds, and this all stemmed from a lack of understanding of the species.
These stories highlight the importance of incorporating good science into management strategies for wildlife. With your help on the Sparrow Swap Project, we will be able to improve our understanding of how different management strategies impact house sparrows and native birds, which will hopefully ultimately lead to better management decisions in the future. By participating, you are providing data and increasing knowledge that will be instrumental in providing effective management for our native songbirds.


If you would like to learn more about the “4 pests campaign in China, check out this article!
If you are interested in reading more about the story of sparrows in general, check out tthis article written by NC State Professor Rob Dunn!

This post was written by Dominic Eannarino, a recent graduate from NC State. You can learn more about Dominic and the rest of the Sparrow Swap Team on our team page.

Sparrow Swap Q & A

On June 13th,2018 we held our first live Q & A about Sparrow Swap! Hopefully there will be more in the future!
You can watch the video here!

2017 Summary Results Handout!

Hello Everyone We’ve created a shareable PDF summarizing our results so far.

Click to download!

Finding the spots!

It’s Suzanne here, and I’ve got some exciting news to share! Last summer a lab out of the University of Seville, Spain released a program called SpotEgg that uses computer vision to find the spots on an egg.

This is a breakthrough for egg color and pattern research. In previous studies spots on eggs were scored by human eyes into broad groups. For example, an egg with no spots might be given a score of 1 while and egg covered in spots given a score of 5. Now, with the help of SpotEgg we are able to quantify exactly how many spots there are, how much area those spots cover, the color of those spots, and color of the background of the egg.

Over the last few months, the Sparrow Swap Team, with the help of one of the SpotEgg creators have been working out the kinks to be able to use SpotEgg to study the color and pattern of our house sparrow eggs. This is the first step to determine whether house sparrow eggs can be used as indicators of contaminants in the environment.

Today, We are excited to share with you some of the first photos from the eggs!

In order to use SpotEgg, we first have to take photos of every clutch using the same camera settings. This includes, a grayscale color card to make sure we can adjust the color, and a scale to be able to determine the size of the spots.

Here is what the photos look like before we run them through the program.

After we inspect the photos to make sure the are of the highest quality, we are ready to use SpotEgg to find the spots. While the computer does most of the work, it is still a tedious process to make sure every photo is correctly photographed, set up in the program, and that the computer accurately found the spots.
There are some few minor details to work out but here is one of our first photos where SpotEgg found the spots.

In addition, the program also creates a black and white version showing where the spots are.

Now let’s Take a closer look at Egg D.
The program has found the edges of the spot by comparing pixels side by side. If there is is a large difference between the two pixels, the computer defines that as an edge. By comparing all the pixels, the program is able to find the spots.

Just to give a you a little taste of the information we can get from SpotEgg, here are some numbers for Egg D.

Spots: 266

Area covered by spots: 44%

Length: 19.7 mm

Width: 16.6 mm

Volume: 698mm3

We are excited to be working on analyzing the photos from the 400 clutches we have in the Sparrow Swap collection over the next few months!

Once the photos are process through SpotEgg, we will be able to begin to look for patterns across the country in therms of color and spots!

Unsure of how to participate in Sparrow Swap?

There are many ways to participate in Sparrow Swap from a one time egg collection to more extensive nestbox monitoring. To help you decide which way is best for you, we’ve created this flow chart.

We hope this helps you find the way to participate that works best for you!


The Sparrow Swap Team

2017 Preliminary Results!


Wondering why we use SciStarter?

Many of you might be wondering why we use SciStarter to manage our project.

SciStarter is a  website where citizen scientists can find, join, and contribute to science through more than 1600 formal and informal research projects and events.  

If you are already participating in other projects like, nestwatch, ebird, inaturalist, or project feederwatch, SciStarter is a way for you to keep track of your contributions to those projects as well as Sparrow Swap.

I’d like to introduce you to some of SciStarter’s features:

Messaging – We are happy to announce that you can now respond to the messages you receive from Sparrow Swap using your email. You can still log-in to SciStarter to see your sent and received SciStarter messages (see photo below). Please note, we cannot receive photos this way. If you need to send us a photo, email us at sparrowswap@ncsu.edu.

Your Profile- Through your profile (see below) you can fill out at a little more about your interests, activities, skills, and instruments.  Once you do this, SciStarter will recommend other projects you may be interested in. Your profile also gives you an overview of the number of projects you are participating in and your total number of contribution to SciStarter Affiliated projects, like Sparrow Swap. Right now, if you complete 3 tasks to complete your profile, you can receive a free ebook “The Rightful Place of Science: Citizen Science!” that features a chapter written by Dr. Caren Cooper, Sparrow Swap’s lead researcher.

Your Dashboard: The dashboard is a place for you to view and manage projects you are participating in. (See Below). 

My Projects, Bookmarks & Events – If you click on the My projects, Bookmarks & Events, you can get a more detailed look into the projects you are participating in. If you have joined a project, and haven’t participated in a while, the “Jump In” will direct you to resources you need to contribute!

We know SciStarter has been changing throughout this season and we appreciate everyone’s patience and feedback as we all have been adjusting to the changes!

If you have any questions or comments, don’t hesitate to ask!


Sparrow Swap Team