Author: David Bradley

Barn Owl pellet

TL:DR – Barn Owls regurgitate pellets containing the indigestible bones and fur from their prey. It is possible to dissect these owl pellets and to find out what the owl has eaten from the debris.

Barn Owl (Tyto alba) hunting over Rampton, VC29If you have ever stopped to think about the gustatory habits of owls, then you have perhaps wondered what happens to all the bones and fur from the little creatures on which they predate after they eat them.

Dry Barn Owl pellet, obtained from WWT Welney

Well, avian digestive enzymes do not have the capacity to break down bones and fur and as the flesh and organs are digested those materials accumulate in the upper gastrointestinal tract forming a hairy bolus, a pellet, that ultimately the owl will regurgitate. A pellet forms after six to ten hours following a meal in the bird’s gizzard, its muscular stomach. Owls and other birds of prey bring up the indigestible material from the proventriculus, their glandular stomach. The pellet is thought not only to get rid of indigestible waste materials that would not pass downwards safely but also to scour parts of the digestive tract, including the gullet to remove detritus that might harbour pathogens.

Single fragmented owl pellet soaking in water

Now, the experimental bit.

I collected an owl pellet (with the warden’s permission at WWT Welney on a recent visit and followed his instructions to soak the pellet in water for a number of hours and then to tease it apart to reveal the bones within its proventriculus, or glandular stomach.

First teasing apart of owl pellet

After about an hour’s work I’d dissected the pellet to reveal a relatively large skull and separated lower jawbones of presumably a vole as well as various femurs, tibia, fibula, scapula, a few vertebrae and lots of rib bones, and perhaps another couple of much smaller skulls the extraction from the of the pellet I did not have the patience nor the equipment to pursue with the necessary care and attention to detail. I did not find any feathers nor insect exoskeletal parts or wings in this pellet. All the remains were rodent mammal.

Rodent (vole?) mandible next to skull extracted from owl pellet

Anyway, I am quite pleased with the produce harvested from my first owl pellet dissection. Mrs Sciencebase points out that she did the very same experiment as a biology student many moons ago.

Boney bits and pieces
Rodent bones after a bit of a cleanup
Rodent skull next to centimetre scale
Rodent jawbones
Rodent lower hindlegs – tibia and fibula

Other birds, including the fish-eating, insect, and carrion-eating birds, grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, dippers, shrikes, swallows, and most shorebirds also produce pellets.

Cranes at WWT Welney

UPDATE: Just over 5 years later, night of 7th November 2024, 83 Cranes into roost at Welney.

There is a flock of 37 Cranes (Grus grus) at WWT Welney in Norfolk at the moment. Some of these have bred on the reserve, all of them, it seems, share their time between this site, NT Wicken Fen, Kingfisher’s Bridge Nature Reserve, RSPB Lakenheath, and the Ouse Washes.

Photos were taken from the Visitor Centre viewing platform, fully zoomed (600mm on a full-frame SLR) and cropped. The birds were about 900m away so the photos are not particularly distinct.

 

Weapons grade chilli dressing

UPDATE: I blitzed them in the food processor today and converted the jar of pickled chillis into a lethal cocktail for drizzling into curries and marinades etc. Thought I had better put a hazmat type sign on the bottle.

Turns out these are Scotch Bonnets, up to 400,000 Scoville units in terms of capsaicin concentration. I’ve now chopped, deseeded and blanched half a pound of them to freeze and pickle.

I wore rubber gloves, a facemask and goggles while I did so, but the house is now full of their volatiles and neither Mrs Sciencebase nor myself can stop coughing and sneezing. I just touched my face with a formerly gloved finger that I thought I’d washed thoroughly and the skin there is sizzling gently…why do we use these weapons on mass destruction in food again, remind me?

UPDATE: I was talking chillis in the pub last night with biochemist and brewer friend Mark. He reckons the best thing to do is blend them up with some salt and white wine vinegar or cider vinegar, seeds and all, to make a useful drizzle to add a bit of fire to anything you cook, as and when. He also warned against adding anything fresh and rottable, such as freshly plucked chillis to oil to make a chilli oil, for instance, as there is a significant risk of botulism with such homemade products unless you add the requisite preservatives that defeat Clostridium botulinum.

Apparently, the chilli peppers I have grown are habanero Scotch Bonnet (1000s times hotter than a jalapeno on the Scoville scale). I chopped one without the seeds into scrambled eggs for lunch and almost couldn’t breathe while they were frying…my stomach is still complaining three hours later, my nose is running, and my lips feel like I’ve been chewing wasps. I only ate the tiniest fragment and none of the seeds. Although there is usually very little capsaicin in chilli seeds its highest concentration being found in the pith that attaches them to the interior of the fruit.

My chillis are now destined for homemade chilli pizza oil, I reckon. I daren’t cook with them again. They’re weapons grade.

In case you were wondering: The Scoville scale is a subjective measure of the heat of peppers, or other spicy foods, basically acting as a proxy for capsaicin concentration. Capsaicin is perhaps the most well known of the many related pungent capsaicinoids compounds in chillis. The scale is named for American pharmacist Wilbur Scoville, whose invented an organoleptic test for chilli heat in 1912. It is still discussed but high-performance liquid chromatography (HLPC) provides a more objective way of testing capsaicinoid concentration.

Capsaicin has the chemical name 8-methyl-N-vanillyl-6-nonenamide) it is a serious irritant to all mammals causing a burning sensation in any tissue with which it comes into contact, particularly sensitive parts of the body such as the eyes and nose, any part of the alimentary tract from top to bottom, and for some unfortunate chilli “chefs” who don’t wash their hands thoroughly after handling, any part of the reproductive tract too…hence the phrase – Chilli Willy – familiar to many waiters in restaurants serving spicy food.

Ironically, capsaicin has been used as a topical painkiller (in shingles for instance) and it has also demonstrated antifungal activity. Indeed, it may well have evolved in the plants for this purpose to protect the seeds, which are dispersed in avian guano (birds don’t feel the burn).

European Robin – Erithacus rubecula

It occurs to me occasionally and I forget to mention it, that this is probably the species of bird we Brits probably picture when we hear the song Rockin’ Robin.

I suspect, however, that the guy who wrote the song, Leon René (aka Jimmie Thomas), was actually thinking of the American Robin (Turdus migratorius), which is like a British Blackbird (T. merulea) or a Song Thrush (T. philomela) but with a red/orange breast.

Anyway, the American Robin’s song is much closer to the refrain “Tweet, tweedle-lee-dee” in the hit, than the rambling and melodic song of the European Robin. One more thing, check out the cover artwork of the record by original Rockin’ Robin artist, Bobby Day, he’s got macaws, parrots, but no sign of a Robin, American, European or otherwise as far as I can see.

Now, here’s a thing…mammals have a single set of vocal folds in the larynx of their trachea. That means they can only really ever bark, moo, yelp, or sing with one voice using that set of vocal folds. The “voicebox” of birds is further down their pipes at the place where the trachea branches into two bronchi. Birds have a syrinx* rather than a larynx, which allows them to create two tones at once.

The European Robin (Erithacus rubecula) is an old world flycatcher. Like I say, not to be confused with the American Robin demonstrating what is possible with a syrinx. Listen out for his neighbours calling at the points in the video when he stops singing. It’s impossible to know who sang first, maybe he’s replying, or maybe it’s them calling back to him.

For Rush fans, yes, that is the reference! The Temples of Syrinx from the 2112 opus. In classical Greek mythology, Syrinx was a nymph and a follower of Artemis, the goddess of the hunt.

Syrinx was known for her chastity, making her the perfect object of worship for the Priests of the Temples of Syrinx who by the year 2112 have banned pleasure (specifically music played on guitars) from the world in deference to computers. In Greek mythology Syrinx was pursued by Pan, the god of the wild and music.

To evade his advances, she fled into the river Ladon, where she asked the gods to turn her into reeds. Pan, of course, took those reeds and from them fashioned his panpipes, ultimately possessing Syrinx for his own pleasure. This myth is why the word syrinx is used for the double vocal flute of birds.

Conkering spiders

I’m not entirely sure why anyone would want to exclude spiders from their home, my preference would be to have a flyeater in each corner of the room to eat the flies. Flies spread disease. Spiders modulate diptera activity.

Anyway, every autumn, the deceived wisdom that putting conkers, the seed of the horse chestnut tree,  Aesculus hippocastanum, around your home will scare the spiders away comes up. It’s evergreen content for columnists. But, it is a myth, it has been debunked several times over the years.

More about conkers coming soon in my Materials Today column.

Moth behaviour

TL:DR – Moths, Lepidoptera, are an incredibly diverse group of insects with some very diverse behaviour. There are some 180,000 known species worldwide with about 18000 of those known as butterflies in the English language, but butterflies are just a class of moth.

There is quite a diversity of behaviour among the moths you see in your trap. The various Yellow Underwings almost all flap wildly around inside until the settle down, but if you disturb them they will flap again, flashing their yellow hindwings.

Large Yellow Underwing (Noctua pronuba)

Others are more passive once they have settled down they stay settled down unless disturbed and will generally avoid gripping on to anything other than the original surface on which they landed, Turnip moth is a case in point it seems. But, others will grab on to an offered paintbrush or piece of leaf and happily clamber aboard to be photographed, Angles Shades, for instance, were happy to do this.

Angle Shades (Phlogophora meticulosa)

Agitate some moths and if they’re not quite warm enough they will sit still but vibrate their wings, revving their engines as it were before taking flight, I’ve watched this with Flounced Rustic, Straw Underwing, Setaceous Hebrew Character, and the Elephant Hawk-moth, which oscillates audibly.

Setaceous Hebrew Character (Xestia c-nigrum)

Many of them will, if disturbed, will have a quick flap before landing on their backs and playing dead. If disturbed again they will flap and fly, if they can. I have observed this intriguing behaviour many times in the last few weeks since beginning my mothing career. Most recently, with the nominate form of The Sallow (Cirrhia icteritia), which I’d gently coerced into a jar to photograph and which ended up on its back staring at me. It quickly flipped back over and took flight into the safety of the shrubbery.

The Sallow (Cirrhia icteritia)

Behaviour that was investigated scientifically not too long ago is even more fascinating than any I have seen in the trap or indeed elsewhere. Most moth species have some form of camouflage that allows them to hide on their favoured vegetation. Apparently, the aforementioned Elephant Hawk-moth likes fuchsia bushes and given how the moth looks and the form of that plant’s flowers, you can see why. The Peppered Moth is said to have evolved to cope with soot-covered trees so that during the Industrial Revolution they became much, much darker and better camouflaged on sooty surfaces. This industrial evolution is most likely #DeceivedWisdom given that this species actually roosts on the underside of leaves where predators  would not see them anyway.

Elephant Hawk-moth (Deilephila elpenor) and fuchsia blossom

Another species investigated recently shows an incredible ability to adjust its position on a tree bark to make itself pretty much completely invisible to putative predators. One has to wonder, how does the moth know what it looks like from above to do this? I can imagine that there are two ways it might be able to carry out this feat. Perhaps the most sophisticated is that its brain has some kind of “map” of how it looks and the moth shuffles around on a surface until the surface matches how it perceives it looks from above.

A second simpler explanation, which occurred to me is that in fluttering its wings gently it can see the shadow beneath them of where the pattern changes and can then simply look to see or feel whether its pattern matches up with the bark surface on which it finds itself. You can read the research here and here.

I contacted the research team to see how and if their work in this areas has progressed and to ask whether my possible explanation for the behaviour had been investigated. This is what the Prof, Piotr Jablonski, had to say:

We have thought along similar lines but did not do any experiments...We thought the by raising and lowering its wings, the moth may compare the colour and/or pattern on its wingtips (visible when raising them) with the colour or pattern of the bark around the moth. This would require changing the colour of the wingtips (probably visible to some moths - but not all - during the wing-raising behaviour) and for it to be able to control the change of colour of the wing area that is not visible. Maybe another student can pick up on this soon...Changku Kang graduated a few years ago.

One other aspect of moth behaviour that has intrigued people for centuries is why moths are drawn to a flame or other light source. The argument is that they use the moon to navigate at night and candles and other artificial light sources confuse them. I don’t think this is true. I have my own theory, which I have discussed here.

Gorse Shieldbug – Piezodorus lituratus

I headed to the garden with my SLR camera and a 90mm 1:1 macro lens to snap what insects I could find while it was sunny. In the end, I finally got around to pruning our wisteria, cutting back the grapevines and the bladder senna plants and the overhanging bramble from our rearward neighbour. I left the overgrowing ivy to bloom for the autumnal insects, including the moths, butterflies, and hornets.

Two hours later, I had no insect photos until I spotted a shieldbug on a leaf in the leaf litter. Picked up on and let him run around our old teak garden table. I’d plucked a few grapes from the vines so plonked one of those in front of him for his close-ups. Needless to say, he didn’t sit still for long and with the short depth of field you get with a macro lens like this it was hard to get a sharp shot on his eyes. Of course, you can use focus stacking to get a greater DoF, but that’s hard with a moving subject like a living insect.

I couldn’t find an exact match for this species and settled on it being a Birch Shieldbug. However, Vicky Gilson on the Bug of the Day Facebook group suggested that it was a Gorse Shieldbug (Piezodorus lituratus). She explained that it is “similar to the Birch but more robust and has a yellow edge to its connexivum. It’s in its late summer/autumn colouration, earlier in the season they are more green.”

That “piezo” prefix in its scientific binomial is intriguing…you can read more about it in my latest column in the Materials Today magazine.

A momentary leps of reason

Regular visitors to the Sciencebase site and associated social media have probably spotted the leps (Lepidoptera, the butterflies and moths), that have somewhat usurped the previous 18 months of bird photography, although that is still ongoing.

Black Rustic (Aporophyla nigra)

If you haven’t, what have you been looking at, then? Anyway, I was almost set to clean up the borrowed actinic light moth trap and return it to my friend who so kindly lent it to me on 24 July and endowed me with a new addiction.

Red-green Carpet (Chloroclysta siterata)

The reason? Well, there hadn’t really been much new for a while and I was starting to believe that our garden setting is not quite good enough for the moths. I persisted, however, and having had a dearth of new species this last week was rewarded on my return from C5 the band rehearsals last night with several I had not seen before as well as some old favourites.

Lunar Underwing (Omphaloscelis lunosa)

Lunar Underwing (Omphaloscelis lunosa)The new ones included Lunar Underwing, Red-green Carpet and Black Rustic, and the oldies, but goodies were the various Yellow Underwings (Lesser, Large, Broad-bordered), Flounced Rustic, Gold Triangle, Willow Beauty, Brimstone, Common Wainscot, Vine’s Rustic, Shuttle-shaped Dart, Sallow, and several others. You can see the 100+moths I’ve identified and photographed in my Leps gallery on Imaging Storm.

Encouragement from the mothing community, especially from Rob, Brian, Samantha, Leonard, Matthew, Karen, Mandy, Ben, Jade (who told me Lunar UW was just around the corner), Mark, and others, particularly on the UK moths Flying Tonight Facebook group. And, of course, Mrs Sciencebase who was not so keen initially, but has taken a flight of fancy of late, a lep of faith you might say.