A Moveable Feast

They say necessity is the mother of invention — I guess that’s why spiders found a clever way to order in, long before Kroger and Amazon began to lug customer’s grub. Not even a Costco cart is big enough to satisfy arachnid appetites but spiders rule when it comes to home food delivery. You see, it’s all about the web.

I don’t mean the Internet.

The menu of ingenious spiderweb designs includes: the classic spiral cobweb with its orderly silk scaffolding; messy 3D tangles rigged between available attachment points; carefully woven sheets scattered like picnic blankets across a lawn; funnels and trapdoors; and even a minimalistic single thread and sticky ball baited with pheromone-mimicking chemicals.  Gourmet or generic, webs deliver the vittles.And spiders are a hungry lot. They have to eat approximately 10% of their body weight in prey, each and every day.  Humans, by way of comparison, consume on average only 2–3% of our body weight—2.5 to 4 pounds of food per day. Now, I can already hear you bellyaching, “Not so fast, Kieran! Sure, 10% may sound like a lot at first but spiders don’t weigh very much. This hardly qualifies as extreme eating.” True, even the 12-inch Goliath Bird-Eating Tarantula is significantly smaller than most people. But, believe me, 10% can add up fast.

Based on published spider censuses (yes, I assure you there are people who do this for a living), there’s an average of 131 spiders for every square meter of land on Earth. Here’s a handy visual for metrically-challenged Americans:  Think of a square kitchen table that seats 4 people. Now imagine that table top covered with 131 peckish spiders. Next, see a vista of spider-covered kitchen tables, placed edge to edge like tiles across the entire landmass of our planet.

Remember, 131 is an average so in less hospitable regions the tables will have only a few patrons, while in other parts of the world each table may have up to 1,000 spiders patiently waiting for dinner to arrive. All told, there are approximately 27 million tons of spiders hanging out in the Earth’s forests, grasslands, plateaus, and deserts, our basements, attics, garages, and kitchen tables.

Before you shudder in horror, remember that insects are the spider-snack of choice and, consider for a moment, how buggy the world would be without these arachnid carnivores.

Scientists Martin Nyffeler (University of Basel, Switzerland) and Klaus Birkhofer (Lund University, Sweden) did just that.  They decided it would be fun to compute the global spider grocery bill and possibly add a peer-reviewed paper to their CVs in the process. They reviewed the work other researchers had done on the metabolic needs of spiders, assessed field reports on the number of prey captured and eaten by spiders, threw it all in a statistical blender, and published their calculations in The Science of Nature earlier this year. According to their recipe, spiders catch and eat 400–800 million tons of prey annually.

Let’s put that number in context, shall we?

  • Seabirds (all species) consume 70 million tons of food annually.
  • Whales (all species) consume 280–500 million tons of food annually.
  • Human beings consume approximately 400 million tons of meat and fish each year.

Still not impressed? Every year, the combined weight of insects consumed by spiders is greater than the total biomass of every person on Earth:

                      7.4 billion people x 130 lbs (avg. weight) = 400 million tons

There’s no doubt spiders play a significant role in managing insects, especially in forests and grasslands. The mere intimidating presence of spiders has been shown to limit the feeding behavior of some insects, reducing plant damage.

Spider prey includes insects that are of interest to humans due to their role as pests or disease vectors, but they’re not particularly helpful in managing agricultural pests.  Nyffeler and Birkhofer hypothesize that cultivated lands have less insect diversity and fewer insects overall than undisturbed lands, making them almost as unappealing to spiders as grocery stores.

Grocers must adapt to modern shoppers, though, and spiderweb technology could help capture the home delivery market!


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© 2018 Next-Door Nature. Originally published in Pest Control Technology Magazine (February 2018). Reprints welcomed with written permission from the author. Thanks to the following photographers for making their work available through the Creative Commons license: Tibor Nagy, Christopher, varmfront.se, Katja Schulz, and Marcus.

Hungry

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Terrier-boy transformed into a velociraptor before my very eyes!

We were walking along, minding our own business, when a momentary ruffling of leaves on the side of the pavement captured Dash’s attention and instinct took over…

head periscopes right…

ears swivel forward, nostrils flare…

field of vision narrows, eyes become lasers…

muscles tense into compressed springs…

in the pause between two heartbeats the chase is on!

 

AND…ended just as quickly by that damned ever-present leash. Grrrr.

 

Initially, I assumed Dash’s prey response had been triggered by a mouse or vole, maybe a chipmunk. Holding him back by the harness, I leaned in for a closer look without really expecting to see anything but fern and wood violet leaves; small rodents usually dive for cover when a predator is on patrol. They don’t risk a backward glance.

So I was surprised and delighted to see small, dark-bright eyes staring back at me from beneath an impromptu stone roof.  Not a rodent after all, but an insectivore. A northern short-tailed shrew (Blarina brevicauda) standing his ground against monsters (Dash and me) larger, in relative size, than a T-rex. Fearless!

Or maybe just hungry.

Thanks to an extremely high metabolic rate, the northern short-tailed shrew (let’s go with NSTS for the sake of brevity) has to eat every 2-3 hours to avoid starvation. That makes for a mighty motivated and efficient predator. I’ll bet you if an NSTS was invited to a screening of Jurassic Park, and saw how much time the velociraptors waste stalking kids in the kitchen, he’d be thinking, “Sheesh… amateurs!” Or maybe he doesn’t need to see the movie. According to the fossil record, shrew-like mammals arrived in time to observe real dinosaurs stomping around on planet Earth. Not this particular shrew of course, but it could be buried deep in his genetic memory.

Finding, catching, and eating earthworms, snails and slugs, spiders, insects, frogs and salamanders, mice and voles, along with some seeds and fungi, is a shrew’s full-time 24/7/365 job. Sometimes they even eat each other. All those meals add up to a daily grocery tab of three times the NSTS’s weight. Think of it this way: if Dash were a shrew, he’d need to eat nearly 65 lbs of food every 24 hours, and if I were a shrew I’d need to eat… well, it’s none of your business how much I’d need to eat.

This voracious consumer tips the scales, barely, at 15-30g (0.53-1.06 oz) but he and his kind are literally red in tooth (and only figuratively of claw). Unlike rodents, a shrew’s teeth do not grow continuously. One set of choppers has to last for their entire life, but red-toothed shrews (Soricinae) have helpful iron deposits that provide additional strength to the surfaces most subjected to wear and tear.

Insectivores are one of only three known living mammal Orders with member species that produce venom. The saliva of a NSTS can paralyze or kill prey, even some animals larger than itself. Nothing as large as a human or a dog, mind you, although the pain of a bite can last several days.

Toxic spit certainly comes in handy when it’s time to appease that insatiable hunger. But before you can bite your dinner, to immobilize or eat it, you have to find it. Often in low- or no-light conditions. Lucky for the NSTS, there’s this thing called echolocation. You would think, given how many terrestrial mammals live at least a partially subterranean life, echolocating would be a pretty common talent. You would be wrong. Only rats, the tenrecs of Madagascar, the solenodons, and three species of shrews, including the NSTS, are known to have this ability. Unlike bats (which, because they can fly, are not technically classified as terrestrial mammals), shrews use low-amplitude, multi-harmonic sounds rather than clicks. It appears these calls are used primarily to collect information about their habitat rather than to zero-in on a food source. Still, you can’t find your way to prey if you can’t find your way.

Even with venom and ultrasonic squeaks, life isn’t a picnic. NSTSs (and shrews in general) have a high mortality rate. Winter is particularly brutal, especially if the shrew in question doesn’t have enough cached food to carry it through the lean times, when mercury itself remains huddled in a bulb-burrow. Summer brings its own set of challenges; temperatures above 95°F (35°C) are deadly for shrews, causing the animals to shift their periods of above-ground activity, interfering with their ability to find their 8-12 square meals per day.

It goes without saying (but here I am saying it anyway) that even fierce predators are often prey as well. Shrews are no exception. Despite spending much of their lives hidden in subsurface tunnels, under leaves, leaf litter, and snow, NSTS become a meal, or part of a meal, for many species of fish, reptiles, birds, and mammals.

It’s a predator-eat-predator world out there and size isn’t everything. You’ve got to stay hungry. As the saying goes, it’s not the size of the dog in the fight that counts, it’s the size of the fight in the dog. Or the shrew. They’re still around, still hungry, and the only dinosaurs to be found are computer generated and animatronic.

I guess that settles any argument over who ruled on Isla Nublar, and who got voted off the island.

 

[Thanks to the following photographers for making their work available through the Creative Commons license: Gilles Gonthier, Goran tek-en, and snapp3r.  © 2017 Next-Door Nature. Reprints welcomed with written permission from the author.]

Town Crier

Hartlaub’s gull [photo: Paul Barnard Fotografie ccl]

My flight into Cape Town landed early last night, just before 9p. That was fine by me since, by that point, I’d been on the plane about 11.5 hours, and in transit from Blacksburg for about 31 hours.  For the next 10 days I’ll be co-leading an international field experience for some of my students in Virginia Tech’s Master of Natural Resources program.

The shuttle pulled up to the hotel and I stepped out into a well-lit courtyard. Then, less than one hour into my first trip to the continent, I had my first encounter with the urban wildlife of South Africa.

I could hear but not see birds overhead. Lots of them.  It sounded like some kind of Corvid, squawking as if they’d just spotted treasure in the form of an untapped dumpster or fresh roadkill.

I checked in at the front desk and headed up to my room on the third floor with every intention of proceeding directly from the door to under the covers. Actually, I detoured to the shower, then bed.  I wasn’t expecting to continue hearing an avian play-by-play going on outside the window but, of course, now I was closer to the commentators’ booth. Still, tired as I was, I knew a few birds weren’t going to keep me awake. I figured the din would die down as soon as everyone settled in to dine.

Boy, did I flub that call.

The birds were still going strong when I woke up this morning so I decided to see for myself who had stayed up all night talking.  Not crows or ravens, as I’d thought. Gulls.  I’d forgotten that the hotel overlooks Table Bay.

[photo: Harvey Barriston, ccl]

Gulls are notoriously difficult to identify to species. They often have several years of varying adolescent plumage before they reach adulthood and stop trying out different looks. For that reason I wasn’t expecting to get a definitive answer when I did a little research on the gulls of South Africa, even though I could see some of them quite well  as they stood preening in the morning sunshine on the roof across the courtyard. Identification turned out to be a snap, though, as there aren’t that many different kinds of gulls here. The urban birds who welcomed me to Cape Town under cover of darkness were Hartlaub’s gulls (Chroicocephalus hartlaubii).

The Hartlaub is a small, non-migratory gull found along the coasts and estuaries of South Africa and Namibia.  Also known as the king gull, and once considered a subspecies of the silver gull (C. novaehollandiae), this urban homebody doesn’t stray far from land, and nearly half of the species’ total population rarely leaves the Cape Town area.

Primarly white with a gray back and black-tipped gray wings, the usually white head is hooded in very pale lavender gray during breeding seasons. The traditional chick-rearing colony is Robben Island, infamous as the place where former South African President and Nobel Laureate Nelson Mandela spent 18 of the 27 years he was imprisoned prior to the abolishment of apartheid.

[photo: Derek Keats, ccl]

Common in its range, the Hartlaub is nonetheless a relatively rare species in the global gull panoply. They’re known for being quite social and talkative in the fall and winter months–that’s right now in the Southern Hemisphere (I can vouch for that assessment). I’ll admit, I felt exonerated for making a faulty ID last night when I read that this gull’s call has been described as “crow-like.”

Hartlaub’s gulls readily habituate to the presence of humans and have learned to exploit our built environment so well they’re considered a nuisance in Cape Town, and a hazard at the local airports (I could have easily waited to learn that nugget of information until after I’m back home).

© 2017 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work  but please ask).

Running start

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American Coot Takeoff (Photo: Matthew Paulson, CC license)

Some birds, including the American coot, need a long water runway to get airborne (Photo: Matthew Paulson, Creative Commons license)

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Hard landings. Anyone who’s a frequent flyer has experienced a few. Always disconcerting, occasionally dangerous. My most memorable touchdown was a trip from College Station, Texas, into Albuquerque on an Embraer ERJ-XXX. I forget which number, but it was one of those 3-seats-across models. One by one, passengers ducked through the doorway and tried to return to their full upright position, only to be temporarily twisted by the low ceiling into a fair approximation of Dr. Frankenstein’s personal porter, dragging themselves down the narrow aisle behind carry-ons in an ungainly but oddly synchronous choreography until each Igor found his or her assigned row.

I crammed my gear under the seat in front of me and strapped myself in right above the left-side wheels, although I was unaware of that fact at the time. It was an uneventful flight with no turbulence to speak of and a clear, bright blue sky. We made our approach, descending slowly as we grew closer and closer to the runway… then over the runway… then

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BAM!!

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Well, I guess the pilot got impatient, or maybe the end of the landing strip was coming up faster than expected, but we dropped to the pavement like a bowling ball falling out of the back of an unzipped travel case. I thought the landing gear was going to come up through the floor and imagined the plane careening along the concrete on its belly in a shower of sparks.

Instead, after a long, pregnant pause, the flight attendant simply welcomed us to New Mexico as we taxied to the jetway. But the cabin, previously humming with friendly chatter, went completely silent and stayed that way until the captain turned off the fasten seat belt sign.

Eared grebe glance (Photo: Jack Wolf, CC license)

An eared grebe in winter plumage.

I was reminded of this experience last month, when I heard reports that 3,500 migrating eared grebes (aka black-necked grebe, Podiceps nigricollis) mistook a snowy Walmart parking lot in Cedar City, Utah, for a lake. The grebes came in prepared for a water landing and, as anyone old enough to walk (and to fall) knows, asphalt isn’t as forgiving as H20. For over 1,500 birds it was a fatal error—some died immediately upon impact, others shortly after. For some who lived long enough to be found by wildlife rehabilitators and good Samaritans, euthanasia was the only humane option.

Even the ones who escaped injury needed help. They were found rowing across the landscape using their wings as oars, getting nowhere fast but too aware of their vulnerable position to do nothing but wait for a predator or scavenger to spot a dark bird struggling against a snowy white background.

6 of 6 Pacific Loon in Distress (Photo: Mike Baird, CC license)

The Pacific (Gavia pacifica) and other loons are true water birds, diving and swimming after fish with speed and grace. But out of water they are unable to take flight, and find walking difficult.

There are a large number of bird species associated with water who need a running start across a watery runway to become airborne, even for short flights; they include grebes, loons (Gavia spp.), rails (Rallidae), diving ducks (Aythyinae; aka pochards or scaups), and many sea ducks (Merginae).

The Utah stranding was unusual primarily for the number of birds affected, but similar groundings happen with some regularity during both the spring and fall migration as well as other times of the year. When I was the director of a wildlife rehabilitation center in Houston, every now and again an American coot (Fulica americana) would be ushered through our doors in a cardboard box. A single bird, usually, or at most two or three. In this case, it wasn’t snow that caused the optical illusion but heat. During Texas summers, hot asphalt roads apparently shimmer like water, at least to avian eyes, so a highway looks like the perfect place to stop for a little lunch and a quick dip, not to mention a long, straight liquid launchpad when it’s time to wing away again.

Canceled flights are such a pain in the neck… and other places, too, at times.

Merganser taking flight 2 (Photo: Mark Dalpe, CC license)

Under the right conditions, some species of waterfowl such as this female common merganser (Mergus merganser), can mistake fields and even roads for water.

Surprisingly, most of these water-walkers did survive their fall to earth. Once grounded, however, they had to hitch a ride to our center. There, we would tend to their cuts, scrapes, and bruises and then give them a helping hand back into the sky by dropping them off at an appropriate body of water. A quick look around to get their bearings and they were on their way, pedaling across the water as furiously as the pilot of a Gerhardt cycleplane but with much better results.

The snow that seduced so many birds into a making a pit-stop in Utah may actually have lessened the devastation by providing a bit of slip and slide to cushion the crash. Happily, International Bird Rescue reports that approximately 2,000 grebes were rescued and released the same week—that’s about as good as it gets in these situations, I suppose.  With any luck at all, they’re now enjoying some R&R and a little southern hospitality.  May they have friendly skies and tail winds for their return flight.

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© 2012 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work; all you have to do is ask). Thanks to these photographers for making their work available through a Creative Commons license: Matthew Paulson (American coot); Jack Wolf (eared grebe); Mike Baird (Pacific loon); and Mark Dalpe (common merganser).

Drummer boy

male pileated woodpecker by ucumari

The male pileated woodpecker may not have the most sophisticated sense of rhythm, but he's a stylish drummer nonetheless (Photo: ucumari, Creative Commons license).

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The holiday soundtrack, which retailers now begin to cue up before the Thanksgiving dinner plates have been cleared from the table, has a limited playlist. Even though the variety of artists covering these tunes is diverse, it doesn’t take long for the music to become little more than background noise. However, there’s one tune that always snares my attention—instantly I’m transported back in time to another Christmas… to a crisp, sunny afternoon on a favorite trail at the Houston Arboretum and Nature Center. That day, the sound of a tree-house being constructed high above my head caused me to  glance up, and I caught my first thrilling glimpse of a not-so-little drummer boy.

female pileated by Syd Phillips cc

The female pileated woodpecker doesn't have the red forehead and "mustache" of her male counterpart.

About the size of a crow (16-19 in. or 40-49 cm), the pileated woodpecker (Dryocopus pileatus) is North America’s largest woodpecker (unless ornithologists can prove that ivory-billed woodpeckers (Campephilus principalis) still exist). At first glance, one might reasonably doubt my ability to determine that this was, indeed, a drummer boy. Adult pileated woodpeckers are easy to identify, but unless you look closely they don’t appear to be sexually dimorphic (males and females of the same species differ in appearance). But I was close enough to see the telltale signs of a male bird—a red forehead and “mustache” to go with the pointy scarlet gnome hat sported by both genders.

Since that first lucky holiday outing, I’ve had the good fortune to see many other pileated woodpeckers, but it’s always a bit of a jolt to the system. Perhaps it’s the combination of size and pointed head, or maybe its the wing-beat pattern during flight, but there’s something eerily prehistoric about this bird. Imaging you are ambling down a wooded path, enjoying the great outdoors but allowing your mind to wander where it will… when out of the corner of your eye your subconscious spots a pterodactylus!

It takes only a second or two for your conscious brain to recognize the error, but not fast enough to prevent your adrenal glands from springing into action, bathing your reptilian brain in fight-or-flight chemicals, turning your heart into a percussion instrument.

Human drummers display a assortment of styles—Afro-Cuban, blues, jazz, zydeco—and the same can be said for the avian set. But there’s not a lot of subtlety to a pileated groove. You can break the beat down into two sets—drumming and tapping.  To my ear, the drumming sounds most like an enthusiastic, albeit novice, carpenter: pound furiously for 2-3 seconds, less forcefully as muscles quickly tire… rest for a minute…  bash the next nail for 2-3 seconds… repeat. Tapping, which is slower and metronomic, often serves as a form of mated pair communication.

pileated foraging hole by Naomi Van Tol ccLooking for signs of pileated woodpeckers in your neck of the woods? It helps to live on the eastern side of the continent, although you can find them across much of Canada and down along a fair bit of the western U.S. coast. This species doesn’t migrate, and once a pair has established a breeding territory they defend it year-round (although they’re a little more relaxed about it during the winter months). So, assuming you’re in the right neighborhood, the next step for spotting this hammer-head is to look for squares. I’m not suggesting these rakishly attired birds aren’t hip—just that they have a stereotypic method of excavating the carpenter ants and wood-boring beetle larvae they like to eat. Unlike many other woodpeckers, pileateds don’t waste time drilling a succession of small holes into tree bark. They gouge out large, roughly rectangular chinks instead; a practice that can be quite damaging to small trees, but it’s beneficial to other bird species who come along and feed on left-overs after the bigger bird has flown the coop.

nestling pileateds by Larry McGahey cc

Pileated woodpecker nest cavities usually have more than one entrance.

Pileated pairs share child-rearing duties, and they prefer to use a different nursery for their offspring every year. That means each April the male carves a new nesting hole, leaving last-year’s crib vacant for other cavity-nesting creatures to use for many years to come. Biologists don’t really understand why some species exhibit nest site fidelity while others do not, but in the case of the pileated woodpecker, this philanthropic service improves the overall health of the ecological community.

All drummer boys—and girls—have a knack for gift-giving, it seems.

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© 2011 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work; all you have to do is ask). Thanks to these photographers for making their work available through a Creative Commons license: Syd Phillips (female pileated); Naomi Van Tol (pileated foraging sign); and Larry McGahey (nestling pileateds).  Thanks also to Marty Stouffer’s Wild America Sound Effects Library for making the recording of a pileated woodpecker’s call and drumming available through a Creative Commons license.

Nutcracker suite

cardinal-grosbeak-crossbill

No, not Tchaikovsky. These are avian nutcrackers (left to right): northern cardinal, rose-breasted grosbeak, and red crossbill. (Photos: ehpien, Conrad Kulper, and Eugene Beckes, Creative Commons licenses)

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Ever wonder why hens’ teeth (and any other kind of avian teeth for that matter) are rare? It’s because teeth are heavy. That’s a problem if you live life on the wing but can’t use a knife and fork to cut your meals up into easy-to-swallow morsels.  A bird’s beak (aka bill) is an adaptation to flight that serves most of the same functions choppers handle in Earth-bound creatures, but without the high metabolic cost of carrying around a set of pearly whites.

Bird Beaks by Shyamal and Jeff Dahl, CC

Figure A. Beak shape and size offers a clue as to what the owner likes to eat.

The beak is a sheath of tough skin on the upper and lower mandibles. Wild birds exploit a wide array of feeding resources and niches, and they are aided in this task by a startling diversity of beak morphology (see Figure A). For example, nectarivores (nectar-eaters), including hummingbirds, usually have long, straw-like beaks that reach deep into flowers. Insectivores (insect-eaters) tend to have narrow, slightly curved beaks that can reach into the small crevices where their prey try to stay out of sight. Piscivores (fish-eaters) have a sharp hook, serrated edges, or both, that help them hold on to their slippery supper. Some of the most distinctive beaks, though, belong to nutcrackers.

The northern cardinal (Cardinalis cardinalis) is a familiar and popular resident of cities and suburbs, possibly because it’s so easy to spot and identify. It’s so popular, in fact, that seven U.S. state legislatures have chosen this species to be their avian poster child.  At  8½—9” (21—23 cm) from jaunty crest to tail tip, it’s a medium-sized songbird with a stereotypic nut- and seed-busting beak—short, stout, and cone-shaped. Cardinal beaks can crush more than seeds, as I can personally attest. From time to time a cardinal would find its way, with the help of a kindly Samaritan, to the Houston wildlife rehabilitation center where I used to work. When this happened, I would stand at the intake desk, teeth clenched, trying to muster enough courage to open the shoebox in my hands.  Now, I like cardinals as much as the next person—I’m from St. Louis, after all, where you can walk down any street in the whole town and know you’ll see someone wearing a shirt adorned with a bright crimson bird perched on a baseball bat. You’d think that would make me an insider of sorts, an honorary member of the family who’s entitled to a few special perks. Hardly. Every time him and her cardinals by Steve Wall ccI’ve held a cardinal in my hand, no matter how gentle the exam or treatment, I was rewarded for my efforts with a throbbing blood blister on my palm, administered by a tiny but furious red vice-grip. Who would have guessed you could feel empathy for a sunflower seed?

The rose-breasted grosbeak (Pheucticus ludovicianus) is slightly smaller (7—7½” or 18—21 cm) with a pale, conical bill reminiscent of the cardinal’s, only more zaftig… a chestnut to the redbird’s hazelnut. Of course, it’s natural for kin to resemble one another, and the RBG is, in fact, one of 17 species known as the “cardinal-grosbeaks.”* Grosbeak—from the French grosbec (gros thick + bec beak) is a bit of a misnomer for this striking black and white bird with a cherry cravat (the females prefer a more sedate, sparrow-like wardrobe). Compared to the schnozzes sported by some members of the Cardinalidae clan, the RBG has a proud but modest snoot. Although not as common as its stop-light colored cousin, human development—and the fire suppression policies that accompany it—have caused forests to sprout where once only grasses grew, allowing the RBG to expand its breeding and migration range westward (although the Rocky Mountains have proven to be a tough nut to crack).  They’ve become a more frequent visitor to backyard bird bistros, where they like to snack on safflower, cracked corn, and black-striped sunflower seed. Insects and fruit are part of their diet as well, but seeds account for the majority of their calorie intake, especially during winter months.

The beak says it all—red crossbills (Loxia curvirostra) are true specialists. At first glance you might think this is a bird in dire need of an orthodontist, but that oddly shaped bill allows them to force open conifer cones and extract the tasty nuts inside. The muscles that allow birds to bite down are stronger than the ones used to open their beaks. But unlike cardinals and grosbeaks, who can clamp down with great force on tough-hulled sunflower seeds (and tender wildlife rehabilitator hands), the crossbill can wedge the slightly opened tips of its bill between the scales of a tightly closed pinecone and then bite down, pushing the scale up to expose the kernel. The red crossbill is extremely dependent on conifer seeds—wildlife biologists refer to animals whose very existence depends on a narrowly-defined habitat or food sources as an obligate species. Most granivores (seed-eaters) start their lives eating protein-rich insects, making a dietary change when they reach adulthood, but crossbills feed on seeds from cradle to grave. Of course, there are risks associated with being a specialist… we’ve all been warned against “putting all your eggs in one basket.” But as long as long red crossbill by eugene beckes ccas you follow the advice of Mark Twain and “watch that basket!” there are benefits as well. For example, red crossbills can raise young any time of the year—even during winter—as long as the cone crop is abundant. I guess some nutty looking adaptations are really quite shrewd.

The Clark’s nutcracker (Nucifraga columbiana) uses the same reliable food resource—conifer nuts—to expand its breeding season. But this member of the Corvidae family (jays and crows) takes the idea even further. It is a hoarder, storing surplus pine, spruce, and hazelnuts. They actually have a special pouch under their tongues to clark's nutcracker by Jamie Chavez cccarry seeds over long distances. A single Clark’s can hide as many as 300,000 pine nuts over the course of a year, and they use this cache crop to feed themselves and their nestlings. Research has shown they have a phenomenal memory and can find most of the seeds they’ve stashed, even months later. Most… but not all; some of the hidden seeds germinate, re-establishing the bird’s favorite trees in areas cleared by fires or logging operations. It’s a sustainable harvest practice, however accidental, and a form of basket-watching that would make Samuel Clemens proud.

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* The grosbeak taxa is a conglomerate of distantly related songbirds known as a polyphyletic (“of many races”) group that we’ll explore in greater detail in future NDN posts.

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© 2011 Next-Door Nature—no reprints without written permission from the author. Thanks to the following photographers for making their work available for use through a Creative Commons license: ehpien (northern cardinal); Conrad Kulper (rose-breasted grosbeak); Eugene Beckes (red crossbill); Steve Wall (male and female cardinals); Trisha Shears (2nd red-breasted grosbeak); Eugene Beckes (2nd red crossbill);and Jamie Chavez (Clark’s nutcracker).  Figure A was made available through WikiMedia by Shyamal and Jeff Dahl.  Bird song mp3s files are in the public domain.