I took the grandkids to Como Zoo, and they watched the orangutans with fascination, maybe because the orangutans were awake and watching the crowd gathered around their enclosure with some fixed stares.
During the last week, I’ve seen several Eastern Tiger Swallowtail butterflies in the backyard. They seem to be especially attracted to the Cup Plant (the same plant the Goldfinches have been tearing apart).
The male color pattern is entirely yellow and black, but without the iridescent blue highlights), so why are there two color morphs for the female?
As I have described in an earlier post, several species of Swallowtail butterflies, and in particular, the female Eastern Tiger Swallowtail, imitate the color pattern of the distasteful Pipevine Swallowtail (a different species entirely).
Predators usually remember what tastes bad or makes them sick, so mimicking something that predators avoid is a good survival strategy. However, that requires that the predators actually have experience with the model (the one being copied), and so far, Pipevine Swallowtails are rare strays in Minnesota because the Pipevine food plants on which their larvae develop are absent here.
We now know that the melanistic (dark form) Eastern Tiger Swallowtail females produce almost all melanistic daughters, and the yellow color morph females produce almost all yellow daughters. So perhaps our melanistic females are offpspring of Tiger Swallowtail butterflies that hatched in nearby Iowa or Wisconsin, where Pipevine Swallowtails have been sighted along with their required food plants.
It’s interesting to note that there is no melanistic female color morph in the Eastern Tiger Swallowtail’s very similar sister species — Canadian Tiger Swallowtails, although the Pipevine Swallowtail has been found in several places in Ontario.
Like many young animals, fledgling Pileated Woodpeckers need to explore what’s good to eat and where to find it. A pair of youngsters completely ignored the suet and seed at the bird feeders, and instead explored a rotten stump.
Without parents to follow around, they must have some innate instinct to look for larvae in rotting wood. I don’t think they found much though.
But who knows, their curiosity might yield a tasty meal.
There is quite a banquet of tasty choices for seed-eaters in the backyard these days, with all the wildflowers trying to set seed. Goldfinches have been attacking the seed heads of the cup plant, tugging forcefully to loosen the seeds that are packed into a dense head. More than a dozen male Goldfinches chirped and chittered as they tore into the plants.
Have you ever wondered how hummingbirds manage to slurp up the nectar in a flower so quickly? Rarely do they pause at one flower for longer than a second or two before moving on.
Occasionally we get a glimpse of a long tongue protruding from their bill when they exit the fake flower on a feeder.
But how does that tongue work to enable them to sip so quickly? Initially, it was thought that the tongue was merely a long capillary tube that drew the nectar up through cohesive action of fluid droplets. But that is much too slow a process.
High-speed videography by researchers at the University of Connecticut has revealed that a hummingbird’s tongue expands rapidly from a flattened ribbon inside the bill to a forked pair of open tubes as the tongue is protruded into a feeding tube or flower nectary. The tongue moves in and out of the bill 15 times a second, expanding and compressing as it moves in and out of the bill, and that pumping action is what delivers the nectar to the mouth so rapidly.
A short video illustrates this much better than I can explain it.
What do you do on a hot, summer day when soft, grassy lawns and the sweet aroma of wildflower blooms beckon? It calls for a short nap in the grass, I guess, even for wildlife, and the backyard was the perfect place yesterday.
In many bird species, males set up and defend breeding territories, and females build the nest, lay the eggs and incubate them — a division of labor that ensures the best possible outcome for their offspring. In other species, both parents feed their chicks; in still others, just the female, or just the male takes responsibility for providing food to the incubating female as well as the chicks. The latter is the case for the ospreys I have been observing at a local marsh.
Males bring the sticks to the nest, the females arrange them, forming a large nest cup surrounded by a foot or two of sticks and even leafy material around the outside. Female osprey perform almost all of the incubation, sitting on those 2-3 precious eggs for more than a month! (32-42 days), rarely getting a chance to fly off and spread their wings. The male brings her food, but she might also get some of her daily energy requirement by metabolizing some of the protein in her inactive flight muscles. (More about the implications of this in the next post.)
The female remains on the nest to protect them for at least another month, although the male might share some of this time with her. Meanwhile, he is the chief food provider, bringing as much as 6 pounds of fish to his brood and his mate on a daily basis.
Once the chicks are feathered out, grown almost to the size of the adults, and able to stand up and move around in the nest, the female takes some time off, and leaves their care to the male. Now he has to not only feed them, but guard them from potential marauding eagles or owls that might like a tasty osprey chick for dinner. (An account of this predatory behavior is described here.)
At about two months of age, having exercised their wing muscles, and practiced “helicoptering” (hovering over the nest), osprey chicks may try a test flight to a nearby tree, where they hang out, still insisting that dad come feed them.
With huge, globular eyes that make up about 50% of their head, dragonflies are amazing visual predators.
And those eyes are key to their success as highly visual predators.
In fact, they are probably the most efficient predators in the animal kingdom, with an astounding 95% success rate per attempt. In comparison, lions are lucky to succeed once every four to five tries and great white sharks only manage to catch what they are after half the time. How do dragonflies do it?
Those giant optical domes on the top of their heads give them a 360 degree view, and contain as many as 30,000 optical units (ommatidia), each with a complement of photopigments that can process images separately. Thus, instead of one retinal focusing area, they have thousands.
In addition, where human eyes have three photo pigments, dragonflies have 15-30 pigments that can detect light in ranges beyond human capability, including detection of polarized light. What if we could see images in UV or infra-red, or whatever other spectral wavelengths dragonflies can resolve?
Photopigments sensitive to blue and UV light are concentrated in the upper part of the compound eye, so that prey (or predators) above them stand out against a perceived white background. Pigments sensitive to longer wavelengths (green, yellow, red) are concentrated in the lower part of the compound eye and allow prey flitting below the dragonfly in dense vegetation to be detected.
In addition to their heightened visual sensitivity and acuity, dragonflies exhibit single-object tracking, which means they keep a particular prey item exactly on a collision course with themselves. (Kind of sounds like a drone, doesn’t it?)
And that’s where the fancy flying comes in handy. To keep the image of the prey in exactly the same place in their visual field, a dragonfly might fly up, down, sideways, backwards, even upside down, if needed. Four wings that can move independently facilitate this maneuverability, and in fact, they don’t even need all four.
These amazing little machines have been around for several hundred million years, feasting on slower flying, less visually talented prey. Such a visual formula for hunting success ensures that they will be around for a while, keeping those pesky mosquitoes in check.
[This is an edited version of a previous post from Backyard Biology]
This week’s extreme heat (high 90s) and high humidity (felt like 90%) are what makes us grateful for MN winters…I guess. There wasn’t much activity in the backyard today, with a only a few birds visiting the feeders and a few bumblebees buzzing in the garden. Dissipating heat is hard for endotherms that generate heat through their metabolism, so it makes sense to find shade, or increase evaporative cooling with a nice bath.
But even the low metabolic ectotherms were fighting the solar load, like this female Blue Dasher dragonfly that tipped her abdomen toward the sky to block the heat radiating down on her sensitive head.