Beach Hangout

We nipped out to the beach after dinner on Saturday. We had a nice walk on our lovely, lonely bit of coastline.

But the beach was busy with youth hanging out (up to no good, probably). Some were alone, and some were in groups, strutting their stuff.

But these youth weren’t your usual crowd of city kids, they were juvenile spotted shags, Strictocarbo punctatus punctatus, also known as spotted cormorants, parekareka, and kawau tikitiki.

Shags were once heavily persecuted as pests. Fisherman believed they destroyed the fisheries, snapping up all the commercial fish and decimating their numbers. Research has shown, however, that their impact on fisheries is minimal. On the other hand, there is some evidence that, in our area at least, shag populations are hurt by commercial fishing. Spotted shag populations on the Banks Peninsula rose from 9,787 pairs in 1960 to 22,123 pairs in 1996 following a reduction in commercial fishing around the peninsula. Illegal shooting can also cause local population declines.

The spotted shag is a marine species, never venturing far from the sea and feeding in deep water up to 16 km from shore. They’re gregarious, breeding and roosting in colonies with up to 2000 birds. The groups of juveniles on our beach were small—a few dozen birds at most. These birds were probably born on cliffs around the Banks Paninsula, and when mature, they’ll head back to those cliffs to lay eggs and rear their young.

So they really were just hanging out on the beach, just like teenagers from Christchurch hang out on the beach on weekends, away from the adults, goofing off and getting takeaways.

Mystery Maggots

Caterpillar, not maggot–see the six true legs and 10 prolegs?

The weather has been hot here, and all the doors and windows stand open all day. With no window screens, that means an array of bugs (and the occasional bird) pops in and out of the house. It’s not unusual to find flies, butterflies, damselflies, etc. on the windows. 

Still, I did a double-take when I saw maggots on my desk the other day. I knew they hadn’t flown in on their own—they must have been hatched nearby. I checked for unseen dead things on the shelves above, but found nothing. There was another maggot this morning, and I did a second unsuccessful check for the source. Then, while I was away from my desk for fifteen minutes, another appeared.

This time I pulled out the microscope and had a closer look.

It wasn’t a maggot at all. It was a tiny caterpillar.

I could think of no reason for a bunch of caterpillars to be living on my bookshelves and dropping onto my desk.

Then I remembered earlier in the day I’d shooed a wasp out of the office several times.

Bingo!

The wasp was a European tube wasp. These little insects seek out cracks and holes to nest in. They fill their nests with up to 20 caterpillars as food for their larvae and then seal the nest with mud.

That would explain the bits of dried soil that accompanied some of the ‘maggots’.

We’ve seen the same thing with our native potter wasps. Last year I had to put tape over all the screw holes in the underside of the dining table, because potter wasps were stuffing them with paralysed spiders (and the spiders kept falling out all over the floor).

As I write, the wasp has returned. Empty-handed this time, she’s fossicking around for a new place to raise her young. Maybe she’ll find one her caterpillars will stay in this time.

Sub-Alpine Idyll

We recently went on a lovely hike up Peak Hill, overlooking Lake Coleridge. The start of the track crosses paddocks, but once on the reserve land, the vegetation changes to a beautiful sub-alpine spread of daisies, Spaniard, matagouri, and tussocks. The daisies, in particular, were spectacular—so many were in bloom that the whole hillside looked frosted. The Spaniard was blooming, too, spiky flower heads rising above the daisies like something from a Dr. Seuss book. Native bees, mānuka beetles, and syrphid flies were all taking advantage of the abundance of nectar and pollen. The air hummed with insects.

You could be forgiven for thinking it was a beautiful, peaceful place. And it was, for us. But among the insects buzzing around were predators—pompillid wasps hunting for spider prey, robber flies snatching unwary insects out of the air, and birds snapping up bugs to feed to their young.

And then there were the plants themselves. At least one hapless beetle impaled itself on a Spaniard leaf. 

It may be pretty, but it’s a rough world out there when you’re insect-sized.

Alpine Delights

The family spent a delightful hour on the Dobson Nature Walk in Arthur’s Pass National Park on Wednesday. The track is an easy one, and hiking it quickly takes about 20 minutes. But it’s not a walk you want to do quickly, especially in summer. It winds through alpine and sub-alpine vegetation, including some beautiful tarns, and in summer, so many plants are blooming, it’s hard to take five steps without finding another lovely orchid, daisy, or hebe in bloom.

For me, the best part of the walk is the abundance of sundews in the tarns. As an entomologist, I’m naturally drawn to carnivorous plants like sundews. Sundews catch insects on the sticky hairs you can see glistening in this photo. The hairs are sensitive to both touch and taste, and when they sense a struggling insect, they fold inward to further entangle their prey. Enzymes exuded by the hairs then digest the insect, and the leaf takes up the nutrients in order to grow in the nutrient-poor alpine wetlands. 

These sundews were just beginning to flower—many plants had flower buds, but none had yet opened. The flowers sit above the leaves—an important adaptation, since the plant needs to be pollinated by the very insects it eats.

The alpine summer is short, so when these plants are done flowering, the leaves will slowly shrink into a structure called a hibernaculum that sits near the soil surface and protects the plant through the winter.

Catlin’s River Walk—a little bit of magic

My family and I were in the Catlins last week, in the southeast corner of the South Island. It’s a wild and remote area, home to more penguins and fur seals than humans. No urban adventures here—it’s a place for outdoor recreation.

One of the things we did was to hike part of the Catlins River Track (we didn’t have time to do the full track). It was unlike any other place I’ve been in New Zealand.

In fact, it reminded me most of eastern Pennsylvania, in spite of the fact that it shares not a single common species of plant or animal.

The track follows the Catlins River, a beautiful waterway that cuts through layers of limestone in one little cascade after another. Swing bridges cross the river several times, providing great aerial views of the water (and a little excitement for those who don’t like heights). The forest is old-growth beech which provides habitat for myriad native birds, carefully protected by intensive predator control. 

In addition to the beech, we were delighted to see two species of orchid on the forest floor, red-flowered mistletoes in the treetops, several species of slime mould, some lovely mushrooms, and a beautiful native harvestman. The birdlife was noisy and varied, but we weren’t lucky enough to see any endangered mohua. And, amazingly, there wasn’t a single sandfly! 

The whole effect was one of an enchanted forest. We were certainly enchanted.

The track is relatively flat—easy hiking for kids or those who can’t face the usual Kiwi hiking track going straight up a mountain, and because there’s no “goal” to reach, you can simply walk as far as you’d like, and then return. The entire length is 12 km one-way, with a return loop option through forestry land away from the river. 

I highly recommend this track. I’ll certainly be going back when I have enough time to do the whole thing.

A Bird in the Hand

I’ve had two funny encounters with birds recently. Two birds in-the-hand, so to speak.

A few weeks ago I was in town, doing some writing in Hagley Park, because it was a beautiful spring day. I sat down on the grass with my lunch and my laptop.

A few minutes later, I noticed a male European blackbird eyeing me up. He hopped closer, stopping when I met his gaze, but then, deciding I was no threat, sidling even closer. My lunchbox sat open between us, and I knew he was sizing it up.

Well, I don’t feed wildlife in general, and I certainly wasn’t going to feed a non-native invasive bird. Besides, I wanted to eat that lunch myself. I finished off my sandwich and started in on my apple.

The bird watched my every move. When I set the apple into the lunchbox to type, he rushed in. I clapped my hand over the box, and he backed off.

The bird was undeterred. When I brought the apple to my mouth again, he lunged for it. He flew up and took a bite out of it while I was biting the other side. His wingtips brushed my cheeks, he was so close.

Well, how could I refuse after that? I gave him the rest of the apple (which wasn’t much more than core at that point, anyway). 

But I made him work for it.

I put it back in the lunchbox, and set the box next to my leg. And that cheeky bird perched on the lunchbox and ate the rest of the apple. Other birds came to see what he had, but none were brave enough to come close, so he had it all to himself. He was terribly smug about it—quite pleased with himself, I’m sure.

My second recent bird encounter happened last weekend. My husband was mowing the lawn, and there was a fledgling magpie in the way. The magpie wouldn’t move out of the mower’s path, so I tried to shoo it away. It still wouldn’t budge, just cheeped at me, as if to say, “Yeah. What do you want?”

So I gently picked it up to pop it over the fence, out of the way. It gave one alarmed squawk, and suddenly its parents were arrowing straight for me from where they had been feeding in the neighbouring paddock. They swooped and screeched as I walked away, and I had to wave my arms over my head to avoid being pecked. The fledgeling, meanwhile, hopped away as though nothing had happened. I could almost hear him chuckling.

So, yeah, I’ve been had by two birds recently. A human in the beak is worth two in the bush, apparently.

A Weakness for Weevils

I was excited to find a new weevil on our property the other day. At least until I identified it.

Meet Otiorhynchus sulcatus—the black vine beetle—pest on a wide range of garden plants, including grapes, black currants and strawberries (all common in my garden).

I admit, I have a weakness for weevils—no matter how much of a pest they are, I think they’re cute. And this one is no exception. She’s lovely, in spite of her diet. And I’m certain she’s a ‘she’, because no males of this species have ever been found. The black vine beetle reproduces parthenogenetically, producing viable eggs without the need for fertilisation by males. 

This ability is the result of a bacterial symbiont in the genus Wolbachia. When researchers in California eliminated Wolbachia in black vine beetles (by giving the beetles antibiotics), the beetles’ unfertilised eggs were no longer viable. It’s a clever little ploy by the bacterium to ensure its own reproduction—only infected insects can reproduce, and they can do so without the trouble of finding a mate (I wrote more about this fascinating relationship in Putting the Science in Fiction and on Dan Koboldt’s Science in Fiction blog).

Another cool feature of the black vine beetle is that it is flightless. It’s not uncommon to find flightless insects and birds here in New Zealand, but it’s a little unusual to see it in invasive pests like the black vine beetle. Native to Europe, the black vine beetle is now distributed all around the world. Pretty impressive travelling for a 6 mm-long flightless insect.

Apparently black vine beetles can cause significant damage to plants. The larvae eat roots in the soil and do the most damage, particularly in potted plants, where root growth is limited. I’ve decided not to worry about them at the moment. I’ve got more damaging pests to worry about, and to be honest, I wouldn’t mind seeing them again. They are awfully cute.