Monday, August 15, 2016

Celebrating the Centennial! 100 years of Bird Conservation

On this date in 1916, the first Migratory Bird Act was signed between the United States
and Canada, serving as the catalyst for a century of bird conservation actions. At the turn of the twentieth century, bird populations were in peril as a result of unregulated shooting for the food and fashion industries. Recognizing the need for collaboration to protect species that traverse their borders, partners in the United States and Canada drafted an agreement to cooperatively manage and protect birds that migrate internationally. The act was the first international agreement forged to protect wild birds, and among the first to protect any wildlife species.

Mom and Dad Decorah don't migrate, but many of the birds we watch do! D1 went to Canada for the summer, while many of Eagle Valley's eagles visit the United States for the winter. North American peregrine falcons have been reported on oil rigs in the Gulf Coast (Candace W/Z, a bird that Bob banded), Chile (the incredible Island Girl), and Costa Rica (the lovely Inmaculada), just to name a few. As Scott Weidensaul says: "At whatever moment you read these words, day or night, there are birds aloft in the skies of the Western Hemisphere, migrating. If it is spring or fall, the great pivot points of the year, then the continents are swarming with billions of traveling birds..."

It is August 15th. Grasshoppers are leaping, goldenrod is blooming, indigo buntings are visiting my feeders, and some of the birds that summer in Minnesota and parts north will begin migrating soon. A great tide of birds will wash down from the north, moving down the Mississippi river towards the southern US, the Caribbean, Mexico, and Central and South America. They will fly over cities, counties, states, provinces, precincts, districts, and nations - a patchwork of histories, languages, cultures, religions, economies, shared experiences, and beliefs - with no passport or knowledge of boundaries other than those imposed by landscape and weather. What has that tiny indigo bunting at my feeder seen? How many miles have passed beneath its wings? What is it like to be an artic tern, which flies about 44,000 miles per year and experiences nearly perpetual daylight as it travels from Greenland to Antarctica and back again? What pulled D1 north 920 miles to Hudson's Bay every summer and what did it feel like when the fishhook of dispersal started tugging her away from the only world she had ever known?

There are a lot of reasons that birds are important. They connect people with nature, which gives us a reason to preserve the landscapes they need. They contribute important environmental benefits, including insect and rodent control, pollination, and seed dispersal. They are an important part of our economy, generating about $500 million annually in direct hunting revenue in my home state of Minnesota alone - and that doesn't count the money spent by birds, bird banders, and people who attend birding festivals. But to me, the most fascinating part of birds will always be their mystery. I am grateful for the window into their world that technology has given us, and for treaties like the Migratory Bird Act to help protect them as they wing their way through our world.

A brief history of three Acts that protect Bald Eagles
The ornamental plume trade provided the catalyst for two of the three Acts that protect bald eagles. In the late 1800s and early 1900s, hats decorated with plumes and other bird parts were a must-have for fashionable ladies. How bad was the plume trade? In February 1886, a young New York ornithologist named Frank Chapman set out on expedition to uptown Manhattan, counting the number of ladies' hats adorned with feathers and other bird parts. Over the course of two trips, Chapman counted 542 hats adorned with 174 whole birds or their disembodied parts. In Chapman’s assessment forty different bird species were represented in his count. As Lapham's Quarterly pointed out, this made uptown Manhattan one of the most diverse bird-watching territories in the world. It is estimated that over 5,000,000 birds were being killed annually to decorate hats and clothing.

Hats decorated with ornamental plumes were a must-have for fashionable ladies! 
Woman wearing a "Chanticleer" hat 
made of bird feathers, circa 1912.
Opera singer Emmy Destinn 
wearing a plume-covered hat, around 1909.

The Lacey Act and the Migratory Bird Treaty Act were passed largely to regulate and combat the ornamental plume trade, which decimated bird populations and drove a number of species to extinction. The Lacey Act, passed in 1900, was the first federal law protecting wildlife. It prohibited market hunters from selling poached game across state lines and was designed in part to stop the flow of feathers from the American countryside to the great millinery centers of New York and London. Iowa fans can be especially proud, since the Act was introduced by Iowa Congressman John Lacey.

The Migratory Bird Act was a landmark agreement signed by the United States and Great Britain in 1916 with the goal of 'preserving those species considered beneficial or harmless to man'. Like the Lacey Act, it provided a tool to limit the extensive ornamental feather trade and the unregulated shooting of birds. Both the US and Great Britain (acting on behalf of Canada, which was part of the British Empire) realized that international treaties were necessary to protect animals with no international boundaries. The two countries agreed to stop all hunting of insectivorous birds and to establish specific hunting seasons for game birds.

The Migratory Bird Act agreement was implemented two years later with the passage of the Migratory Bird Treaty Act of 1918. The act established penalties for people who broke the law, making it a crime to pursue, hunt, take, capture, kill, or sell a migratory bird or any of its parts, including nests, eggs, and feathers. This effectively shut down the ornamental feather trade and gave species like the snowy egret a change to rebound.

Breeding plumage: Far better on the snowy egret!
By Len Blumin from Mill Valley, California, United States (Snowy Egret display) [CC BY 2.0 (], via Wikimedia Commons
While bald eagles were covered under the Migratory Bird Treaty Act, they hadn't been directly affected by plume hunting. But sport shooting, bounty hunting, and habitat loss were another matter. The Bald Eagle Protection Act was enacted by Congress in 1940 to protect the bald eagle from direct hunting and habitat encroachment. As the territory of Alaska demonstrates, we haven't always admired bald eagles. Between 1917 and 1952, 128,273 bald eagles were killed and submitted to the Alaska Territorial Treasurer for bounty. We have no figures for the amount that were simply killed offhand or to provide feathers and parts for the trade in "authentic" Native American artifacts, but Congress felt that an act was needed to protect the bald eagle from extinction. The Golden eagle was added in 1962, amending the law to the Bald and Golden Eagle Protection Act.

While there are many complicated issues around the Migratory Bird Treaty Act (consider the controversial proposed bald and golden eagle take proposed by the Fish and Wildlife Service) it has saved millions if not billions of birds since the initial treaty was signed in 1916. Let's celebrate the act and keep moving forward to save birds for the next 100 years! Migratory birds need our help: as Steve Holmer, Senior Policy Advisor for the American Bird Conservancy, pointed out: "Forty percent of all migratory bird species are in decline, so it is urgent that we put in place practices we already know will save birds from needless deaths.”

The Fish and Wildlife Service has a long list of important conservation messages. I chose my favorite ones to post here! Remember, times change, and threats change with them.

What is the main threat to migratory birds? 
  • Habitat loss due to urban development, agriculture and other human activities is the main threat to migrating birds. [Note: 'other human activities' is probably referring to global climate change].
  • Migratory birds depend on suitable breeding and wintering grounds and stopover sites where they can rest and feed along their migratory routes. The loss of any sites used by the birds during their annual life cycle could have a dramatic impact on their chances of survival.
What can we do about it? 
  • Conserve habitat - conservation works! Where we have invested in healthy habitats, birds are doing well. Healthy birds mean healthy forests, wetlands, grasslands, shorelines and oceans [and healthy forests, wetlands, grasslands, shorelines, and oceans mean healthy birds].
  • By conserving birds we conserve our American landscapes and the economies and ways of life that depend on them. From farmers and ranchers to outdoor recreationists to children, we all benefit when birds thrive.
#birdyear #thenext100years

Friday, August 12, 2016

Eagle tracking: can you do something about the tracking antenna?

We were asked a lot of questions about eagle tracking during After the Fledge. D1, D14, Four, and D24 and D25 are part of a study by biologist Brett Mandernack from Eagle Valley: the first and, to date, most extensive tracking study in of free-living eagles in the Upper Midwest. Brett’s transmitter and field research have collected a wealth of data about the migratory, wintering, and summering behavior of bald eagles.

The most commonly asked question involved the PTT antennae located on the eagles’ backs. Could they be removed or shortened? How do the transmitters work and why are they the length they are? This blog attempts to answer those questions. Warning: it requires a fair amount of reading and has a long resource list at the end!

Can you get rid of the antenna?
We cannot. An antenna is needed to transmit data from the PTTs worn by our eagles. The PTT and GPS units from Geo-Trak Inc. collect and encode data about location, heading, speed, time, activity, and transmitter and battery performance. The encoded data is supplied as energy to the antenna, which radiates it as UHF radio waves to the Argos satellite network orbiting 528 miles (850 kilometers) over our heads. From there, ground stations receive real time data from the satellites and retransmit it to regional processing centers where we can access it. No antenna = no data.

Why can’t the antenna be smaller? Couldn’t it be part of their leg bands?
Let’s start with a quick primer. When we talk about radio waves, we are really talking about a small part of the electromagnetic spectrum - the range of all types of electromagnetic radiation (EMR). EMR is classified by wavelength into radio wave, microwave, terahertz (or sub-millimeter) radiation, infrared, the visible region that we perceive as light, ultraviolet, X-rays and gamma rays.
Our transmitters are talking from eagles on the ground to satellites in space using radio waves with a frequency of 401.664 MHz.  As the chart above shows, the higher the frequency, the shorter the wavelength. The shorter the wavelength, the smaller the antenna. So if a higher frequency means a smaller antenna, why aren’t we broadcasting at, say, 30GHz – the top end of the radio spectrum? An organization called the International Telecommunication Union coordinates the shared global use of the radio spectrum, which includes assigning radio frequency allocations for space communication. 399.9 - 403 MHz is the band that ITU has allocated for navigation, positioning, time and frequency standard, mobile communication, and meteorological satellites. Geo-Trak’s satellite tracking products use the Argos satellite network, which transmits and receives data at 401.650 MHz (± 30 kHz). Argos is using the highest frequency available to them.

So why does frequency impact antenna size? The wavelength of a frequency is the distance an electromagnetic wave travels to complete one cycle. As the image at right shows, a 401.664 MegaHertz signal (a signal that oscillates, or moves through a complete cycle 401.664 million times in one second) has a full wave length of 29.38 inches, a half wave length of 14.69 inches, and a quarter wave of 7.34 inches.

For the antenna to radiate properly, it needs to match either the full wave or one of its major harmonics. Therefore, 7.34 inches – a quarter wave - is as short as the antenna can be and still function. Perhaps improvements in materials, circuitry, and/or manufacturing will someday allow smaller antennae to be used in satellite tracking, but for now, a whip antenna is our only choice for robust ground to space communication.

The image at left shows an electrical wave oscillating through a full wave antenna, where the antenna is the same size as the wavelength. If the antenna were longer or shorter than the wavelength it is propagating, it would work less efficiently or not at all. A dipole antenna breaks the wave into two pieces, so it can be half as long as a full wave antenna. A quarter wave antenna - the kind used on our PTTs - breaks the wave into four pieces and can be a quarter the length.

I found the distance traveled to be quite fascinating. If you do the math, 29.38 inches (the distance it takes for our signal to complete one cycle) multiplied by 401,664,000 cycles per second equals roughly 186,000 miles per second. It takes a lot less than a second for messages to travel from the Dynamic Duo (D24 and D25) to the Argos satellite system 528 miles overhead.

Will electromagnetic radiation of an antenna hurt the eagles?
No. Terms like electromagnetic radiation are frightening, but not all electromagnetic radiation is harmful. Innately dangerous electromagnetic radiation is found in the high-frequency end of the spectrum, since high frequency waves are a lot more energetic than low frequency waves.  Think of it this way:  gamma rays have frequencies of 1 x 1021 Hertz, which means that the wavelength crests, or hits its highest potential energy point, 1 sextillion times or cycles per second. That packs a punch! By contrast, visible light has a frequency of around 5 x 1014 (500 trillion cycles per second), microwaves have a frequency of 1 x 1010 Hertz (ten billion cycles per second), and our radio waves have a frequency of 4 x 106 (400 million cycles per second).

Power is also a factor. I have a 1500-watt microwave oven that can damage living tissue. However, it is literally almost 7000 times more powerful than the 225mW solar units that power the transmitter. Even cellphones produce radio waves that are more powerful and energetic than ours.

What about insect studies? Those antennae are really small!
A lot of really cool work is being done with insects. While some of the technologies involve active transmitters, which require batteries, others use passive devices like RFID tags and geolocators. Passive devices don’t require much power and can be made extremely small. A couple of links:
Unfortunately, passive devices can’t transmit. Researchers don’t get data unless the animals move in close proximity to a reader (think of a feeding station where animals might gather), or they are recaptured for a data download. Geolocators could be used to track migratory peregrine falcons that return to the same nest box year after year, but they aren’t a good fit for tracking juvenile or sub-adult eagles that wander unpredictably and often widely.

The tiny little transmitters used in tracking insects are very cool – check out that tiny backpack! – but they have short battery lives (7-21 days) and a limited tracking range on the ground only (100-500m). As neat as they are, they aren’t suitable for tracking juvenile and sub-adult eagles either.

In short…
We can’t get rid of the antenna, which is as short as it can be given the frequency of our ground to space transmission. Argos did a great job designing a package that is light, safe, reliable, and trackable almost anywhere on earth, especially given the physical requirements of the transmission system. The transmitters do not harm bald eagles or impact their social or reproductive interactions with eagles that aren’t wearing transmitters. Passive devices aren’t a good option since juvenile and sub-adult eagles range unpredictably and often widely before settling down to nest, while tiny active devices have short battery lives and a limited ground-only tracking range – something that won’t work for animals that can fly hundreds of miles and live relatively long lives.

However, research into insects and small birds is driving tracking devices to become even smaller.  If at some point appropriate tracking hardware becomes available with a smaller antenna, we will use it.

Did you know?
The wavelength and frequency of electromagnetic waves are closely related. If you have a frequency, you can get the wavelength, and if you have a wavelength, you can get a frequency. With the wavelength, you can determine the length of the antenna you need to transmit or receive radio waves at a given frequency. The formula looks like this:  Wavelength = Wave speed/Frequency.

Let's say that I have a frequency of 401.664 MHz, or 401,664,000 cycles per second. The wave speed is the speed of light, which can be expressed as 3x108 m/s or 300,000,000. If I divide 300,000,000 by 401,664,000, I get .7468 meters. Since I was raised in the English system, I immediately convert it to inches or feet, which gives me an antenna length of 29.38 inches. This was very helpful when trying to determine why the antennae on our PPT systems are the length they were. This web calculator provides lengths for half and quarter wave antennas if you want to play around with making them:

What could you do with an antenna? There is a community of people that listen to the earth via homemade VLF radios. This website provides an introduction to the concept and some online streams:

Resources that helped me learn and write about this:
Since you made it to the bottom, I hope you enjoy this bonus image. XKCD explains the spectrum as only they can!