Nongeographical Migrant Traps

Dave La Puma, over at woodcreeper, had some smart analysis today about local scale movements of migrant passerines, and how that may account for reports of new arrivals even following nights of unfavorable weather. The premise is pretty straightforward; lacking favorable conditions to move on, birds are likely to shift from areas of substandard habitat to prime foraging grounds. Remember that a migrant trap typically works by virtue of its geographic location. The classic example of course is Cape May island, essentially the bottom of the bird funnel that is the state of New Jersey. With thousands of birds packed in to such locations, its only a matter of time before competition, or merely a need to seek more fertile feeding grounds, disperses birds across a wider area. Often the tried and true migrant traps are left desolate. If you don't believe it, goto Sandy Hook after four days of south winds sometime this autumn.

Understanding what makes up prime foraging habitat can make your birding more consistent. No longer do you have to wait for those perfect cold fronts, you can take advantage of "slow days" by visiting sites that concentrate migrants left in the area during the last wave. To follow up on Dave's post, I thought I'd give a quick punch list of the sort of attributes that tend to be common among such locales. Of course these aren't hard and fast rules, but sort of a general set of guidelines.

1. Diverse habitats. Lots of habitat types will provide prime foraging for a greater number of different species. Paulinskill Wildlife Management Area; a locale I like, contains upland forest, open woodlands, meadows, shrubby tangles, a riparian corridor, a freshwater wetland, etc. Equally important are the edges. Its a well accepted pillar of ecology that an edge between two ecosystems tends to be more diverse than the interior of either (the edge effect). A sunlit edge between forest and field is precisely what I think of when asking myself, "where would I find lots of warblers?"

2. Structure. Much like diversity across the landscape, lots of variation in a forest profile can be the difference between poor migrant habitat and a productive birding area. Birders are very familiar with the strong preferences some species have for a specific band in the forest spectrum, such as the Mourning Warbler (almost always associated with dense thickets <5 m above the ground) and the Tennessee Warbler (an infamous source of neck pain). The more strata you take out of the forest, the fewer species you can expect to find. Even for birds with a more generalist approach to the forest profile a diverse structure is beneficial, providing more feeding and roosting opportunities.

3. Oaks. Really any native trees, though Oaks are certainly among the most productive. Such trees are absolutely teeming with insects. Your average oak can support more than five times as many insect larvae than a tree not native to the northeastern United States. Why? Well, I've discussed this at length before. Oaks, by virtue of their evolutionary roots in this region, support a far greater number of different species of insects.

4. Fruit. As the breeding season marches on, fruiting shrubs and trees become incredibly important sources of food for migrant birds. Cold weather snaps may kill off insect food sources before later migrating species, such as Black-throated Blue Warblers, pass into our area. These birds have adapted an ability to switch their diet over to primarily fruit (as opposed to obligated insectivorous species such as Cerulean Warblers, which as a result have to migrate much earlier). Areas with lots of fruiting shrubs and trees can be magnets for migrants. Celtis (Hackberry), Prunus (Cherry), and Cornus (Dogwood) are just a few native genera that are especially favored.
Though it is worth noting that the nativity of the fruit does not matter much. You can certainly see migrants feeding on Ligustrum (Privet), Lonicera (Honeysuckle), Rosa multiflora (Multifloral Rose), and other invasive plants. In fact, passerine migrants likely play a big role in moving invasive species from one region to another. Aralia elata (Japanese Angelica Tree) a newly emerging invasive species in the Midatlantic region, seems to be (based on pure anecdotal evidence only) distributed primarily along major migration routes in New Jersey. If you go to the parking lot of the Chimney Rock hawk-watch in September, you can witness dozens of birds gorging themselves on Aralia berries.

5. Sun. This, for me, was an overlooked ingredient of prime feeding habitat until last fall. Look for the little spots that: (1) get sunny the earliest in the morning and (2) stay sunny latest in the evening. Even a little increase in air temperature will get insects moving and birds from hundreds of yards away will converge on the area.

So thats it, five things to look for when seeking good foraging habitat. Of course this is only a starter list, so if anyone has additional suggestions please leave a comment. Make sure to get out and find some feeding sites, then check them on that next slow day. You may end up pleasantly surprised!

a few migrants around

There were signs of southbound migration around yesterday, though they were few and far between. A slight increase in the number of singing Peewees around our house in Stockton as well as Bull's Island State Park, a lone female Scarlet Tanager making a brief appearance in the backyard, and a few dozen Chimney Swifts (some of which are probably still the locals) made up the most obvious evidence on a round of casual birding. Friday I saw my first fall Osprey, hunting on the lakes at Duke Farms. That bird was certainly a migrant; we never observe local birds using our lakes during the breeding season.

As a recent Hunterdon County transplant, I haven't yet figured out the local hotspots for migrant passerines. I suspect that the Stockton area, situated on flat land between two small ridges, may be a bit of a dead zone but it'll be great to put that theory to the test. I suppose it will depend on how many birds depart the ridges in favor of moving down the river. A similar effect can make the Delaware river corridor in the Walpack Valley (western Sussex County) excellent under the right conditions. Strong easterly winds would probably push birds off the Sourlands and right into our area as well. Probably the key will be finding the geographical features and prime feeding habitats that will concentrate migrants. I have a few hunches, I'll be sure to post reports as I check them out. In the mean time, suggestions would be appreciated if you're familiar with the area!

Year in Life

I had my 'its that time of year again' moment this morning, when I spotted a dark juvenile Merlin perched atop a telephone pole on my way to work. Upon arriving, a coworker remarked that two Harriers were coursing our grasslands that morning. The grasslands, last week alive with fledgling Ammodramus sparrows, are silent save for the occasional 'jimp' of a lingering Bobolink or the rattling alarm call of a Meadowlark. Most of these birds have passed on as well. Our fields peaked at nearly 50 Meadowlarks in one day two weeks back and they've been in short supply ever since. Autumn is here.

'Autumn?' you say, 'but its only August!'. That's true, but other species have no regard for the Julian Calendar and a good naturalist must remember that. I count the day I ceased to pay attention to seasons as defined by solstices and equinoxes and instead began to follow the cues of migrants as one of my greatest revelations as a birder. It was then that I realized I was missing more than half of migration!

To me, the greatest joy in naturalism is gaining insight into the sychrony of the landscape and the organisms that use it. The flight of migrant birds does not occur unassisted; it times perfectly with swells in insect populations and the ripening of fall fruit. Predatory birds come along for the ride, dependent on the big concentrations of their small cousins to better chances of obtaining a much needed meal. In a great choreographed dance the whole food chain rolls down the continent, leaving the landscape to sleep behind it, and the animals that remain behind to eke out a living until the whole thing happens again.

You don't have to go far to find something extraordinary about nature. A Black-throated Green Warbler foraging in an Eastern Hemlock will do. Such a scene tells a story; of bird, insect, and tree in a relationship rooted in time and sustained for millenia. A single thread in the tapestry of life that defines a year in nature. Endless delight awaits those who take the time to pay attention to it.

Pictures

Just a few pictures I snapped this weekend. Most of these were taken around my "pollinator garden". I use the term very loosely; its only three plants. One purple giant hyssop, one anise hyssop, and one narrow-leaved mountain mint.



A spring peeper perched on a hyssop leaf, laying low in the hot part of the day. Do you think it was coincidence that this is where it happened to choose? I doubt it, this plant was teeming with insects. Backyard food chains in action!



This daddy longlegs (thats the scientific name right???) appeared to be nectaring at hyssop flowers. I've always thought this group was strictly detritivorous, so if anyone has any insight I'd love to hear it.



One of about ten species of hymenoptera (bees, wasps, etc) frequenting my plants.



a dog-day cicada

more on invasives

Following up on my post yesterday, I had two thoughts about adjustments that could be made to the jargon that might avoid misconceptions about the ecology of biological invasions

1. Think of the alien species problem not as a series of unrelated 'invasions', but as an overall homogenization of the world's biota. On a global scale, thats exactly whats happening. Sometimes you hear people refer to non-native plant introductions as environmentally beneficial, as they 'increase biodiversity'. Even if you allow for this to be true on locally (which I would contend it usually isn't, not to mention the fact that biodiversity alone is by no means an accurate yardstick of ecosystem health), what we are seeing across the planet is rapid range expansions by certain groups of organisms, with regionally endemic species losing out. Some of these changes in distributions are driven by changing climate patterns, but others are directly linked to humans shuttling species all around the world for one reason or another.

2. The use of the term 'native plant'. The meaning is far too nebulous for someone who does not come from a science background. Also, as demonstrated by Mike Pollan's article, it incites erroneous accusations of secondary motives and a desire to keep nature 'pure'. I can't say I have a catchy new term in mind, but it would have to frame a species' place in relation to it being vital for the ecological integrity of an area. If anyone has any suggestions, leave a comment!

Invasive Plants- its not evolution

"So why aren't people just another means of plant dispersion? Isn't the spread of non-native species just an example of an organism evolving into a new environment?" If ever there was an argument invasion ecologists would love to put to bed, it is that one. Though never reaching wide acceptance, this idea has existed in the gardening world in varying degrees of extremity for as long as the term 'invasive plant' has been known beyond the realm of theoretical ecology. Such arguments usually run along the same theme: the case against non-native plants is at best anti-humanist and at worst an expression of latent xenophobia. The argument is summed up quite nicely in "Against Nativism", a New York Times article by noted science writer Michael Pollan from 1994. It may not be quite fair to hold words written by Mr. Pollan, whose books I quite like, fourteen years ago against him (though he apparently reconfirmed his convinctions more recently in the blogosphere). But I only read the article recently, and its a good medium from which to make a few points.

I'm going to leave the philosophizing aside. Of course such conjecture about the extent to which humans should influence the natural world is a value judgement. In a broad sense, I actually agree with quite a bit of this article. There are roughly fifty thousand introduced plants in use throughout the United States. Of those, only a fraction are considered invasive, with as few as thirty marked as high conservation priority in New Jersey. Many naturalized weeds confine themselves to old lots and other waste places, such as the wild carrot to which Mr. Pollan refers. Such plants can hardly be thought of as invaders and, much like the House Sparrow, their global distribution has become part of the story of human immigration. Of course one can say, "well they still occupy a place a native plant could be", but ultimately their impact is miniscule compared to more pressing issues.

But what of the thirty that do not behave themselves? Here, Michael Pollan's argument takes a turn that took me by surprise. Here's what he had to say:

"There's no question that these migrations are sometimes destructive of the ecological status quo, if indeed such a thing even exists. But migrations of species by whatever means is an abiding part of natural history; in any event, they're almost always irreversible. Turning back the ecological clock to 1492 is a fool's errand, futile and pointless to boot. It seems to me we gardeners would do better to try to work with the mongrel ecology we've inherited -- to start out from here."

Coming from the champion of food production as a complex system, I was struck by the over simplification implied in this statement. An ecosystem is a mind-bogglingly complex thing, this we've already established. To suggest that a plant out of its ecological context, free of its natural predators, pests, and competitors, will merely be a blip in our region's natural history seems incredulous. Its like throwing a rock at a glass house and not only expecting the house to rebuild itself, but to find a useful place for the rock as well. Can we truly call this evolution? I would argue that we can't. To me, evolution is the sum of a species' trials and tribulations, the series of influences that defines its niche. In absence of this, is a species truly evolving? In a strictly biological sense of course, but in an ecological context its role becomes boundless and therefore meaningless. A different word is in order, and 'invasion' certainly describes what happens quite well.

I am also bothered by the suggestion that human transport represents merely another form of migration. I don't think it is quite that simple. While I'm sure there is a myriad of reasons one could point out as to why thats true, a big one come to mind for me. First of all, these introductions are not random. Most invasive plants were purposely selected and brought here for horticultural purposes. Given the harsh nature of formal landscape, a species' resilience is often heavily considered. I wrote more about the ecological issues associated with this idea here, so I wont go into detail. But if we accept that this "human selection" plays a role in vetting invasive species, how can such a 'migration' be akin to movement by wind or water? Mr. Pollan is right to say evolution will draw no distinction, but he fails to consider the fact that we've already taken care of this before a plant can even make it to the natural environment.

Ecology is very much a "sum of all its parts" concept. I certainly do not prescribe to the idea that humans play no role in shaping the natural world, but I am skeptical that moving plants between natural environments at distances of thousands of miles constitutes a helping hand or represents a natural process. The level of disruption is too great for me to accept that it is merely a change in status quo. Trying to frame the results of biological invasion in philosophical argument stems from a failure to recognize that we as a species are quite capable of being a negative influence on the natural world. If believing such makes me anti-humanist, than so be it.

Anyway, I'm sure there will be more on this later. For now it is a great day and I'm going back outside.

vegetables

It must be mid-summer...here's a picture of one week's haul from our CSA (Community Supported Agriculture) share at Honeybrook Organic Farm. For those not familiar with the concept, a CSA is sort of a group investment in a farmer's success. Share members pay a lump sum prior to the growing season, fronting the farmer capital to run the operation, and reap the benefits in the form of weekly vegetable shares all season long. It turns out to be a great deal...ours averages under 30 dollars a week. Of course earlier and later in the season the volume is nothing like the picture above, but I've been consistently impressed with the volume of food we've received. If you're interested in buying your food local (which you should be) it is a great way to keep costs down.

Posting about vegetables may seem like an aside from my blog's focus, but it really is not. In fact, I made this post so I could discuss exactly that. I've touched a little bit on how connected our food production is to the natural world in a previous post about grassland birds. Lately, 'buy local' has been heavily touted throughout the green world, though usually in reference to savings in energy (the amount of oil involved in producing food on an industrial scale and shipping it from centralized growing locations, often not even in this country, is truly astronomical). However, small operation organic farms can also act as exceptional natural places, particularly for pollinating insects. The plight of the European honey bee has been well publicized. The major declines in our native pollinators; bees, wasps, beetles, butterflies, moths, bugs, etc has not. Where are these native insects going? They're succumbing to habitat loss.

Suburban sprawl has all but vanquished the meadow from New Jersey's landscape. What little of such habitat remains is usually (you guessed it) choked with invasive species and non-native weeds that provide substandard food for native insects. I'm sure you wont be surprised if I say that deer don't help, following the same pattern as with woodlands, eating the natives and passing up the invasives. Of course, you see little patches of native flowers here and there, especially this time of year, but crucial links between these habitats have been destroyed. These little isolated patches of flowers are inhabited by little isolated populations of insects. Without the ability to mix with other populations and breed the survivorship of such insect species is greatly diminished.

This example is illustrative of an ecological concept called the metapopulation; essentially a 'population of populations'. The interactions between populations, also called metapopulation dynamics, is crucial to species survival. Individuals leave one population and travel to another. Upon arrival, they breed with individuals outside of the population from which they came. Such links are crucial for maintaining genetic diversity and are severely compromised when habitat is overly fragmented. The very reason grassland birds are doing so poorly in New Jersey is because we have severely damaged these links by isolating populations beyond distances individuals are capable of traveling. The exact same thing is happening with native pollinating insects. The difference is that the path to their conservation is much clearer.

So this is where the organic farmers and backyard gardeners come in. We can't all create a grassland, but we can all provide pollinator habitat. Field margins on small farms can can easily and cheaply be planted with native wildflowers. In exchange, insects will be happy to pollinate vegetable crops as well. These patches of dense native vegetation also serve as shelter for predators, beetles such as ladybugs and others, that devour plant pest insects by the thousands. Free pest control! The same principles can be applied to a home garden, plant an edge of native vegetation on one side and reap the benefits. Before long you'll find yourself making a bee line (ha ha) for the flowers as soon as you get home, just to see who's hanging around. A lot of these little critters are really, really cool looking.

Our culture has a tendency to separate the natural world from the spaces in which we inhabit, whether its through rejection or assumption that nature can't integrate. That simply isn't true and the survival of our local biota depends on that notion coming to an end. We need to bring nature into our yards and farms; to de-sterilize our lawns, landscapes, and row crops. Doing so will help reconnect the 'wild areas', the green spaces and preserved natural lands that dot New Jersey's landscape.

The way we produce food in this nation currently is a deliberate attempt to step away from the natural world, to remove the vagaries of environment from the equation. I don't think its coincidental that as an industrial food chain fed the suburbs, the suburban landscape likewise became obsessed with symmetry, cleanliness, and an obsessive desire to simplify the environment as much as possible. Boiling down the incredible, wonderful complexity of the natural world into a series of logical, orderly steps is a failing enterprise. If we accept what I said at the beginning of this piece, that our food is inexorably linked to the natural world, than the same is true of the industrial food model. In the future, buying local may cease to be a virtuous act of those concerned with such issues and instead become a practical necessity.

So what do you do with three bowls of tomatoes, weighing in at 8.5 lbs (especially when you expect the same amount next week)? Slow roast and freeze them for the winter! Winter tomatoes always come from Mexico or somewhere else where food eaten in New Jersey really shouldn't. Besides, shipping a tomato that kind of distance really results in a tasteless and mealy experience. Cover a baking sheet with aluminum foil. Half small tomatoes and quarter large ones, and arrange them cut side up on the sheet. Preheat your oven 225 F. Sprinkle tomatoes with olive oil and salt, pepper, and herbs (thyme or oregano) to taste. Let roast until they're done (trust me, you'll know). This is a project to start in the morning when you have all day. Pack in quart-size tupperware containers or ziplock bags and freeze. The insects will thank you.

If you're interested in reading a more thorough and better written account of the ideas I've begun to lay out here, check out Bringing Nature Home by University of Delaware entomologist Doug Tallamy.

Pictures from Cushetunk Mountain

I finally remembered to upload my pictures from a visit to Cushetunk Mountain a month or so ago. This little nature preserve is part of the Hunterdon County Parks system and is definitely worth a visit. It has some of the healthiest, most intact forest I've seen in New Jersey, let alone in a largely suburban county like Hunterdon! It really is truly amazing.















You don't have to stray off the trail to find a variety of native plants; this picture was taken pretty much right at my feet! Geranium maculatum (Wild Geranium), Arisaema triphyllum (Jack-in-the-pulpit), and Amphicarpa bracteata (Hog Peanut) flourished. There was numerous Galearis spectabilis (Showy Orchis) as well, though we had missed their bloom time.


















The understory was amazingly intact. It is difficult to see in this picture (I truly am a lousy photographer) but pretty much all of that green is Viburnum acerifolium (Maple-leaved Viburnum)! This shrub, once the dominant component of the understory in central New Jersey forests, has all but disappeared due to intense levels of deer browse.


















A bunch of Maple-leaved Viburnum seedlings. Another striking feature of this site was the high levels of recruitment (seedling survival). In deer disturbed forests, seedlings are rare. Very few of them manage to make it through their first several years of growth, after which they will be above the "browse line" and less susceptible to deer damage. As a result, there are no trees to fill canopy gaps when elders fall. These gaps tend to stay open and fill in with weedy invasives.


















Taken from the same spot as the photo above, but with a wider perspective. There is SO MANY SEEDLINGS! Not just viburnum, but also plenty of Quercus (Oak), Acer saccharum (Sugar Maple), and Carya (Hickory).



















This shot shows a pretty good healthy forest profile. Note all the layers: ground level thick with seedlings and herbs, low shrubs, high shrubs, lower canopy trees, and the big guys looming overhead. Now think about the last patch of woods you were in and compare. If it was in New Jersey it was probably something like: stiltgrass, barberry, nothing, nothing, canopy. That simplification of forest structure doesn't just mean doom for native plants, it interferes with the forest's functional capabilities and provides low quality wildlife habitat.


















Cimicifuga racemosa (Black Cohosh) inflorescence, before bloom. I liked this picture so I'm including it!


In conclusion, GO! This weekend. In fact, go right now. Everyone with a vested interest in preserving New Jersey's biodiversity and natural beauty needs to see this place. Human involvement in restoring function to our forest ecosystems has become a necessity in this state, and areas like Cushetunk Mountain provide an excellent baseline. They are also great points for interpreting goals of ecological stewardship. Most of us have heard the "restore to what?" argument against Restoration Ecology before. There is sometimes a misconception that the goals of the discipline are rooted in time, and it is driven by a desire to recreate an 'untouched wilderness' in New Jersey, a snapshot of what the landscape looked like before humans arrived. That couldn't be further from the truth. Its also not an obtainable goal, since New Jersey has never not been inhabited by people in its post ice age ecological context, but thats another story entirely. We strive to restore ecosystems to function, to reintroduce the plants, create spaces for the creatures that inhabit them, and allow for balance with soil and air. Perhaps it is better to think of it as healing, seeking to encourage healthy environments upon the landscape you're given. We all know of wildlife rehabilitators, so just think of environmental stewards as ecosystem rehabilitators!

Directions and more information can be found here. I have no idea how Hunterdon Parks manages their land, but they're doing something right! Cushetunk is only one of several very nice areas they own. Lastly, on a completely unrelated note, here's a photo of a katydid I took as it waited out the day on my narrow-leaved mountain mint. Again, I just really like this picture.