Why Migratory Birds Ignore Puxsutawney Phil

I for one am tired of the cold. Don't get me wrong, this winter in Delaware has been great. We've had an abundance of snow and few days of freezing rain, but this Texans had enough. I was raised on a steady diet of 6 months of hot, 2 months of cold, and 4 months that are only kind of hot. By mid February it's time to start buying swimsuits and stocking up on suntan lotion.

Punxsutawney Phil the Perpetrator
  (Alessandro M.)

Unfortunately, I don't live in Texas anymore. Punxsutawney Phil, the infallible weather muse, has predicted six more weeks of winter for the east coast. We'll forget for a second that our rodent friend is less than stellar at prediction and take his words at furry face value.

Just 2 weeks from now, the lucky residents in Texas will herald their first of the season main land migrants, and in 3 weeks every gulf state from Texas to Florida will see their very first migratory species. This may sound early to some of you, and indeed it is, but certain individuals in a population will try to get an early start to their breeding season. These include the southern breeding species like the Golden-cheeked Warbler, southern U.S wintering warblers like the Northern Parula , the early gulf migrant Louisiana Waterthrush, and the seemingly always migrating Purple Martin.


This winter has been brutally cold. We've seen record snowfalls in the south, and the great lakes ice coverage at it's highest extent since 1994 (90%). If this years weather and our furry friends ominous prediction is right, these early birds will be in a heap of trouble. So why would an individual migrate early when its still cold and how do birds cope with the wildly inconsistent weather in spring?

The extent of the ice on the great lakes this year (noaa.gov)

Lets start of first with an easy question:
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Why even show up early?
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Birds benefit from arriving early in a variety of ways. They get the best pick of territories, avoid predators, and have more chances to succeeded. All of this equates to better breeding success (the chance of successfully raising chicks to adulthood).

Males arriving to a breeding site first get the best pick of territories. If these males choose the highest quality habitat, they'll have an easier time feeding their nestlings. This increases not only an individual chicks chance of surviving, but increases the numbers of chicks a pair can raise.

Common predators for nesting songbirds include snakes and raptors (birds of prey). The time of the highest nest predation coincides with the middle of the breeding season. Nesting hawks have to forage more as their own nestlings grow up. This increases predation as the seasons progresses. With the progression of seasons, temperatures heat up, leading to more snake species migrating out of their winter dens. This all culminates in peak nest predation in the middle of the breeding season. Earlier migrants can skip this dangerous phase by nesting earlier before these factors peak.

Most songbirds nest multiple times in a season until they finally succeed. Some crazier birds may even renest after they've succeeded in raising the first nest.  In the case of Willow Flycatchers, some parents begin nesting before the first brood is even able to fly! So, with an early start to the breeding season, you get not only more chances to succeed, but more time to raise even more young!

It's clear, there's a real advantage to showing up as early as you can.
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What could possibly go wrong?
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Well mainly weather.
The top weather-related killer of birds is the cold. Untimely snow storms routinely kill birds who aren't prepared. Particularly wet snow can quickly saturate a birds feathers, forcing it to land freezing and wet. Situations like this kill even hardy snow birds. It's no surprise that species who aren't used to cold temperatures regularly die of exposure when an unseasonal cold front penetrates into the south [1].

Ice can also be particularly tricky for birds. Waterbirds, like ducks, require open water to feed. When all available water is frozen over, many starve before they can find water. Because of this, ducks often fly hundreds of miles south in search of open water in the winter. This permanent relocation leaves many of us in the Northern States (yah I just said that Auriel) with a lack of ducks for the rest of winter.

Surf Scoters, Indian River inlet, DE

Birds who usually experience extreme weather are well adapted to it. It's when temperate birds run into this weather that there becomes a problem. These birds spend the majority of their time in warmer locations and tremendous amounts of energy flying thousands of miles north to breed. These exhausted tropical vacationers are ill suited in maintaining their internal temperatures. In spring, spending a night below 10 degrees Celsius (50F) costs a songbird the same energy as flying for 3 hours. [2]. To a small song bird that's ~90 miles! [3].

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So what keeps them from showing up early?
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The range map of Golden-Winged Warblers

Migratory birds react strongly to temperature. The correlation between the average temperature at a migrants wintering grounds and summer grounds is both fascinating and complicated (We'll go indepth on this at a later date). Many studies have shown some species won't migrate north unless it's certain temperature.[2][4] Unseasonably cold temperatures in spring are usually brought about by a cold front from the north. This all but guarantees the northern latitudes are also cold. Migrants can dictate their future weather patterns by monitoring temperatures and delaying their departure till situations improve.

The pattern of migration is generally where southern migrants move through first and northern populations arrive later.  This keeps migrating birds at a manageable latitude, but can lead to highly incongruous breeding seasons. A warbler breeding in the southern Appalachian Mountains in late April has entire month head start over it's twin breeding all the way in Canada in June.


Despite evolutionary traits, some birds still fly straight into bad weather.

Last year, a late arctic blast ran straight through the Midwest. Migrating rails, already on their journey, were faced with frozen wetlands with no where to go. Lucky for them, these hardy wetlands species have adaptations to survive in conditions similar to this. Rail species like the Virginia and Clapper rail are routinely found all the way into Delaware and New Jersey in winter. The northern most breeding rail, the Yellow Rail, breeds just shy of the arctic circle. Their bigger bodies, water resistant feathers, and terrestrial foraging allows them flexibility when it comes to surviving temporarily in variable temperatures.

Two Clapper Rails taking the ice in Delaware raily well

If a birds particular tolerance or adaptations fail, we unfortunately find large scale mortalities.  In March 1904, an estimated 1.5 million birds were found dead buried in the ice and snow after a blizzard in Minnesota. In 1964, 100,000 king eiders died when water ways refroze in the spring. This impact can sometimes be quite extreme on populations. A study populations of cliff swallows in the great plains, lost 54% of their population when unseasonable weather hit the region in 1996 [1].

This extreme consequence acts as a natural checks and balances system for  birds. Nature maintains a hard line that punishes birds that arrive at the wrong time.  Without it, birds would casually move their timing earlier and earlier.

Interestingly, we're actually seeing migratory timings shifting earlier in the spring. Over all global warming trends have lead to earlier plant blooming and migratory bird timing. We're seeing not only earlier migrants but northern range expansions of sub-tropical species into the north. Clearly the cold hasn't stopped them. [5][6].

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Migratory timing is a large field in science, and this article has just touched the tip of the iceberg. We haven't for example mentioned birds being tied to high concentrations of bug activity, or the consequences of freak storms (hurricanes and tornadoes) on migrating birds (my masters research ;)). Clearly there's a lot for us to get to and always more to learn.

If you have any questions or would like to suggest a topic we cover, feel free to email us at naturalausterity@gmail.com

-Boone
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[1]Newton, I. (2007). Weather-related mass-mortality events in migrants. Ibis, 149(3), 453–467. doi:10.1111/j.1474-919X.2007.00704.x

[2]Wikelski, M., & Tarlow, E. M. (2003). Costs of migration in free-flying songbirds. Nature, 423(June), 2003.

[3]Alerstam, T., Chapman, J. W., Bäckman, J., Smith, A. D., Karlsson, H., Nilsson, C., … Hill, J. K. (2011). Convergent patterns of long-distance nocturnal migration in noctuid moths and passerine birds. Proceedings. Biological Sciences / The Royal Society, 278(1721), 3074–80. doi:10.1098/rspb.2011.0058

[4]Gauthreaux, S. A. (1991). The Flight Behavior of Migrating Birds in Changing Wind Fields : Radar and Visual Analyses. American Zoologist, 31(1), 187–204.

[5]Gordo, O. (2007). Why are bird migration dates shifting? A review of weather and climate effects on avian migratory phenology. Climate Research, 35, 37–58. doi:10.3354/cr00713

[6]Marra, P. P., Francis, C. M., Mulvihill, R. S., & Moore, F. R. (2005). The influence of climate on the timing and rate of spring bird migration. Oecologia, 142(2), 307–15. doi:10.1007/s00442-004-1725-x

Bird Questions: How Do Birds Survive Cold Weather?

When the polar vortex descended into the United States in early January I got questions from several friends concerned and curious about how the birds would deal with these conditions. To help answer that curiosity we bring you the first installment of Bird Questions.
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Cold weather challenges birds ability to survive in several unique ways. While many species of birds migrate to avoid these challenges other species have developed physical and behavioral adaptations that allow them to not only survive but thrive through the winter months.

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Physical Adaptations

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Feathers
Feathers make birds adaptable. Birds can live in some of the most extreme environments because

feathers are so good at helping birds thermoregulate (keeping their bodies at a comfortable temperature). Feathers are remarkable because they help all birds stay comfortable, no matter what climate they are in. For birds spending the winter in cold places they have many more down feathers which work to keep them warm. 

Down feathers are small and have loose barbs which trap warm air. The down works like a warm insulating layer and on top there are feathers designed to keep out the wind and the water. These overlapping feathers work like shingles, shedding water and deflecting wind. This combination works much like the layers that people wear in the winter to keep warm, they trap in warm and keep out the cold.  

Diagram of counter current heat exchange 
http://freewebs.com/gta101/arterieskw99.jpg

Legs and Feet

Most birds don't have feathers on their legs and feet which leaves them exposed Heat sinks are parts of a system where heat is lost. Counter-Current Heat Exchange  is used by birds to to minimizing their heat loss and preventing any damage to their feet from the cold.

Counter-current heat exchange works because birds arteries are wrapped around the veins in their legs. When these two vessels come in contact it allows the incoming warm blood from the heart to heat the cold blood coming from the feet. Exchanging heat prevents the bird's core from having to work as hard and keeps the feet from freezing. 

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Behavioral Adaptations

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Constant Feeding

Birds can gain and lose weight more easily then people. Many birds, especially small ones will spend most of their time during cold weather feeding [1]. Crazed feeding allows them accumulate enough fat to make it through the next night. Many birds will spend all of their day light hours eating or looking for food when the weather is cold. Songbirds probably spend most of the day actively searching. Their need for food is the reason you see them pile onto birds feeders. Smaller birds have higher metabolisms then raptors so they need more fat for how big they are. These large fat reserves laid down every day will be burned off overnight due to their high energy requirement. Raptors will often revert to the least energetic method of searching for food. Raptors may soar or spend time just perched looking out for prey items.

Posture

Just like how a Northern Cardinal can change the position of the feathers in its crest, birds can change their body posture and feather position to keep themselves warmer. By puffing up and making themselves as round as possible birds conserve the most warmth. As a bird forms a more round shape the ratio of surface area (outside of the bird) to the volume (the body of the bird) changes so the surface area is minimized for a particular size of bird. By minimizing surface area the amount of heat which can be lost is limited and puffing up their feathers helps limit heat loss even more.

Birds have a very aerodynamic shape and by orienting themselves to face into the wind the wind passes over them quickly. This is especially important in wet environments since down feathers lose their warmth when wet. By facing into the wind the birds feathers can work like shingles and shed the rain, protecting their warm downy undercoat.

Bluebirds huddling for warmth (Michael L. Smith)

Night Roosts
Several species of birds have been documented to huddle together in the winter, often in cavities or nest boxes to keep warm [2, 3]. These flocks are typically the same species, but are not necessarily related family members. Both Eastern Bluebirds and House Wrens are known to do this. Providing shelter for roosting birds is one reason to leave birdhouses up over the winter. 

Torpor
Most people are familiar with hibernation, but some bird species engage in another method of surviving daily torpor. Torpor is a bit different then hibernation, individuals come in and out of it on a daily basis, rather then a season one. Their body temperature is also not lowered as much as individuals who hibernate. It still serves the same purpose, lowering your body temperature means you have to use less energy to stay warm, If you were to encounter a bird who was in torpor it would probably appear to be sleeping but would not quickly awaken as you approached. This slow response to disturbance is one reasons individuals probably don't to into torpor every night, it leaves them more vulnerable to predators and other hazards, but when cold weather strikes it can be a valuable tool [4].

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How You Can Help 

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While birds don't NEED your help to survive the winter, during extreme weather there are a few things you can do to assist birds in surviving cold weather.

High Quality Food - Suet might seem a little odd, since it's basically just animal fat with seed mixed in, but it's pure energy to many bird species and can be a very high quality food source. More important then the kind of food you put out is to decide whether or not you will be feeding all winter. If you not, its best to taper off the food in the fall instead of just stopping in the middle of a snow storm when birds may have difficulty scouting out alternative food sources. 

Shelter - Plant evergreen shrubs (plants which keep their leaves or needles year round) around your yard so birds can find protection from the wind/rain/snow. To prevent your bushes from being used as cover for predators (such as cats) keep the bushes back from feeders and bird baths. 

Water - Staying hydrated is just as important as food, and often more difficult to find. You can use a heater or dripping water to keep a bird bath open. During the winter it's often best to put sticks or other perches around the bird bath since birds wont want to actually bathe in cold temperatures. These perches allow them to get easy access to a drink. 

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One of the remarkable things about birds is their ability to survive extreme conditions. Take some time over the winter and watch your local birds at the feeder and see if you catch them exhibiting any of these adaptations. And if you have any other bird questions drop us a line - naturalausterity@gmail.com

- Auriel

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[1] P1.101  Friday, Jan. 4  Do small wintering birds adjust their metabolic performance in response to perceived level of cold? MILBERGUE, M.*; BLIER, P.; VEZINA, F.; Univ. of Quebec in Rimouski; http://www.sicb.org/meetings/2013/schedule/abstractdetails.php?id=738

[2] Mayer, L., Lustick, S., Battersby, B. (1982) The Importance of Cavity Roosting and Hypothermia to the Energy Balance of the Winter Acclimatized Carolina Chickadee. International Journal of Biometeorology. Volume 26:3 p231-238 http://link.springer.com/article/10.1007/BF02184939

[3] Kendeigh, S. Charles. (1961) Energy of Birds Conserved By Roosting in Cavities. The Wilson Bulletin. Volume 73:2 p140-147 http://www.jstor.org/discover/10.2307/4158912?uid=36852&uid=3739536&uid=2&uid=3&uid=67&uid=36848&uid=62&uid=3739256&sid=21103359393693

[4] Geiser, F. and Ruf, T. (1995) Hibernation versus Daily Torpor in Mammals and Birds: Physiological Variables and Classification of Torpor Patterns. Physiological Zoology. Vol 68:8 p 935-966 http://www.jstor.org/stable/30163788

How to Enjoy Cold Weather

Even sub-zero days offer great opportunities
to explore. UP of Michigan December 2013 (Auriel Fournier)

It's -47F with the windchill, my jeep barely starts, my lungs hurt, but eventually the jeep stops squealing and we're on our way for another day of birding. When we planned our long weekend of birding in northern Minnesota I promised Matt the cold 'wouldn't be that bad' (since it normally isn't). So he bought his plane ticket in balmy October on my promise of great birds.

January 2nd arrives and twelve hours of delays later he arrived in Wisconsin with no luggage, just the coat on his back and a polar vortex headed our way bringing some of the coldest air in 20 years. Luckily we are all very flexible travelers and between Nick and I, we had enough warm clothes to convince Matt he wouldn't die and we headed to Minnesota.

We worked with the weather, made lots of changes along the way and our trip was a success. We didn't spend as much time outside as we planned and ended up doing most of our birding from the car, but we had a great time and all of us experienced winter in a new way. That -47F degree morning though with the wind blowing and all of us wearing so many clothes its hard to move I thought we were a little bit crazy. Then the sun came up, the beauty of northern Minnesota showed itself again and we managed to stay pleasantly warm because we were prepared for the conditions.

Typical winter days offers even more possibilities. When you dress for the weather, a hike on a single digit day can be just as enjoyable as one on a fall afternoon. Being cold outside is easy. I've been there many times. I went to school in the Upper Peninsula of Michigan and I made every rookie mistake before finally figuring out how to enjoy winter like a yooper. Today I'd like to show you some of those mistakes and how to fix them so you don't make them yourself. Not all of us need to do a 12 mile snowshoe with frozen pants and no feeling in their legs to learn these lessons.

With a little bit of knowledge anyone can dress to be comfortable in the cold.

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Layering
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Layering keeps you warm and is simple once you know the basics. You need to wear clothes to hold in the warm air and block the wind. Once you've got on good layers there are just a few additional things to remember. Know your body and dress accordingly. If you are like me and your hands/feet get cold easily put more layers on your arms and legs to compensate. Always ensure your layers overlap at your neck, waist, wrist and ankles. These overlapping layers seal in the heat and will prevent cold air from leaking in.

I always err on the side of wearing too much, since you can always shed a layer. You can also do a quick check when you first get outside, stand for a moment and see if you can feel the cold air seeping in. If you can then you probably need an additional layer or to adjust what you are wearing. 

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Equipment
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Outer Layer - The purpose of an outer layer is to keep out the cold and wind, usually through a heavy winter coat. If you don't have one, a rain coat along with several layers of sweatshirts and sweaters underneath can work. Layering doesn't just apply to your core, keeping your legs warm is important, and is probably the most neglected part of layering. You don't need to go buy fancy snow pants, you can cheat and wear a pair of rain pants with thermals/sweatpants layered underneath.

Base Layer - Wear loose clothes so they can trap air between the layers and a close fitting base layer to keep you feeling warm and wick away moisture. Most people will tell you to get a fancy synthetic shirt, and if you can afford Underarmor, wonderful. Cotton long underwear can also work just as well. Thermal base layers can be picked up for $5-10 at Wal-mart. Grab a top and bottom layer (remember not to forget your legs!).

Hats - Even if you are not a 'hat person' you need a hat. Otherwise your body will spend valuable energy replacing all the heat radiating away. Style isn't important, so find something cheap. A good hat will cover your entire head, the thicker the better. You can get hats for $5-10 at Wal-mart.

Gloves - You'll be warmest with a giant pair of well insulated gloves, but if you have to write things down, or really do anything, they might be cumbersome. There are many styles of gloves suited to different tasks. Some have flaps that flip back and become fingerless so you can use your hands. Your best bet is something with thinsulate. If you have to remove your gloves often get a thin pair of gloves to go underneath.

Scarf -  Scarves keep all the warm air around your core while preventing heat loss from your neck, another large heat loss area. Scarves can be worn different ways to help keep the wind off your face, which is great when wind chill is a concern. Just make sure you find something soft enough so it won't irritate your face.

Vests - I personally am not a vest person, but if you often find yourself being too warm vests can be a key layer because they keep your core warm without over heating.

Boots -  If you're going to be out hiking, or building a snowman a good pair of hiking boots and some thick socks are probably all you need. Make sure your boots aren't too tight. Tightness restricts the socks/shoes ability to trap warm air around your feet and makes your feet cold fast. Wearing a double layer of socks works really well to both keep your feet warm and prevent blisters but wearing more then two pairs can cause additional issues with not allowing space for warm air to be trapped.

Socks - Good socks are worth investing in. I love Smartwool, but there are now lots of brands of comfy wool socks out there, so shop around. Wool is important because your feet sweat. In your daily life you probably don't notice, but when you wrap your feet up in socks and boots the sweat does not evaporate. Leaving you with cold feet. Wool keeps you warm even when its drenched, which is why wool makes great socks.


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Extreme Weather 
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When the weather really cold it's important to take care of yourself. Check in with your group members and make sure everyone is staying warm. Take breaks, warm up inside, make sure you eat enough.

The first big issue with extreme cold is wind. Wind chill makes cold dangerous, FAST. Check out the wind chill chart from the National Weather Service. If the wind is strong at all you can come under danger of frostbite very quickly. The best way to combat the wind is to keep all of your skin covered, especially your extremities (hands, feet, ears, nose) and stay active so you keep pumping lots of warm blood to those regions.

Bond Falls, UP of Michigan
(Auriel Fournier)

The second big danger is water. Now chances are if its super cold out there isn't much open water for you to interact with, but most of us live in places where cold means something around freezing, which often leaves things wet and sort of slushy. Once you get wet its really really hard to stay warm unless you are wearing special clothes. Above when I say you can get away with cotton I mean you need to stay dry. No wading through streams, no falling through the ice, no standing in the freezing rain, no sliding down winter waterfalls. If you are going to be doing something where there is a good chance of you getting wet then you need more specialized equipment which is often not cheap but is well worth it. Being cold and wet is dangerous, please be careful. 

Please use this info to help yourself enjoy the outdoors, not push yourself to dangerous limits. When the weather is extreme always make sure it's smart to be out doing what your doing. Several days of our trip we planned to be out snowshoeing all day, which at -30 or -40 is not safe, so we changed our plans and did short hikes (<15 minutes) and explored in the car. Sometimes an alternate plan for the day may be in order and that is OK. Part of the wonder of the outdoor world is the extremes of its weather and experiencing them is fun, but don't throw caution to the wind. A five minute experience can be more then enough for the conditions.

Most of the time though the weather is more mild and dressing for the weather is fairly easy. It may take a bit of trial and error before you get layering perfect, but the rewards are fantastic. Winter is (in my opinion) the most beautiful time of year and winter offers opportunities for exploration and recreation you can't do in any other season. Being active all winter helps fight winter depression and opens your up to 12 months of fantastic adventures! So pull on some extra layers and get out there!