Bird ringing course at New Holme : 2 to 10 September (Part 2) : “rare is common and common is rare!”

Part 1 described the first five days of the bird ringing course at New Holme. Part 2 describes the last few days and does the overall wrap up. Let’s do the wrap up first. During the course, we handled 367 birds of 35 species. Species in red have links to extensive descriptions with headings: identification, habitat, distribution, behaviour, … The number before the species name is the number handled.

  1   Pale Chanting Goshawk
  3   Kittlitz’s Plover
  1   Three-banded Plover
  2   Blacksmith Lapwing
  1   Curlew Sandpiper
  2   Little Stint
  1   Ruff
  1   Burchell’s Courser
  3   White-backed Mousebird
  1   Large-billed Lark
  1   Spike-heeled Lark
130   Grey-backed Sparrow-lark
  1   Stark’s Lark
  1   Red-eyed Bulbul
  1   Capped Wheatear
  1   Sickle-winged Chat
  1   Cape Robin-chat
  1   African Reed Warbler
  1   Rufous-eared Warbler
  1   Neddicky
  4   Levaillant’s Cisticola
  3   Cape Wagtail
  5   Southern Fiscal
  2   Bokmakierie
  7   Wattled Starling
 11   Pied Starling
 40   Cape Sparrow
 33   Southern Masked Weaver
 45   Red-billed Quelea
 30   Southern Red Bishop
 21   Lark-like Bunting
  4   Karoo Thrush
  2   Eastern Clapper Lark
  4   Karoo Prinia
  1   Southern Grey-headed Sparrow

The most striking thing about this list is that rare is common, and common is rare. The six most caught species account for 81% of the total. These six species are 17% of the total number of species. So 17% of the species make up 81% of the total. Rare is common and common is rare. We get back to this theme at the end of the blog!

Of the 367 birds handled, 35 were retraps. Three of the retraps were birds ringed in 2019, and 27 were ringed last year, 2022. The remainder of the retraps were birds ringing during the course, and retrapped on a later day of the course. A retrap rate approaching 10% is impressive. As we continue the ringing effort at New Holme, we will start to be able to use the data for estimating survival rates, at least for the common species.

The highlights of our activities on Days 1 to 5 of the course were summarized in Part 1. Species handled included Burchell’s Courser and Pale Chanting Goshawk. It was hard to believe that there would be species that would trump these.

But let’s go back to the Pale Chanting Goshawk first. One of the questions that we get asked most often by people who are watching ringing for the first time is: “Do the birds make it back into the wild?” We ringed the goshawk on Tuesday. On Saturday we took photographs of this bird at two places a couple of kilometres apart on the New Holme farm.

Pale Chanting Goshawk with ring at the New Holme Bird Ringing Course
Pale Chanting Goshawk with ring at New Holme Bird Ringing Course

This is the only ringed Pale Chanting Goshawk at New Holme. The diameter of the ring is selected by first measuring the diameter of the leg. The chosen ring size must be able to slide up and down the leg easily, but must also be relatively snug, so that things cannot entangled between the ring and the leg..

Days 1 to 5 were covered in Part 1!

Day 6 : Thursday 7 September

We had to wait until after dinner for the birds of the day! We’d put mistnets up along the edge of the dam at dusk.

Curlew Sandpiper New Holme Bird Ringing Course

If you look at the upperparts of this Curlew Sandpiper, you can see a few feathers in breeding plumage on the bird’s back – these are the dark chocolate brown feathers, edged with cinnamon and white. The non-breeding plumage is a nondescript grey. The primaries, the main flight feathers, have covered at least 30,000 km, the straight-line distance from South Africa to the breeding grounds on the Siberian tundra, in the Taimyr Peninsula, directly north of India in Asia. They still look in pretty reasonable condition. There ought to be 10 primaries, but if you count them you can see only nine. That is because the 10th one, counting from the outside has been dropped, and is being replaced by a new feather. The secondaries bend a bit towards the bird’s body, and there appears to be a bit of a gap between the primaries and the secondaries. That’s where the growing feather ought to be. The moult of the primaries proceeds slowly from the inside to the outside of the wing, in such a way that there is never such a big gap that the bird can’t fly. The process takes about four months to complete. By early next year, this bird will have a new set of primaries for the northwards journey to Siberia to breed and then back again afterwards..

Besides this Curlew Sandpiper, we handled other long-distance migration waders: Little Stint and a Ruff.

We also caught a Blacksmith Lapwing, a resident wader:

Blacksmith Lapwing New Holme Bird Ringing Course

Most birders never get to see the spur at the points of the wings of a Blacksmith Lapwing. This bird’s spur was 11 mm long. That makes it a female. The spurs of the males can be as long as 20 mm. They are as sharp as needles. One of the privileges of being a ringer is seeing these kinds of features from close up!

Day 7 : Friday 8 September

We didn’t have to wait long for the bird of the day. At 09h35 the message arrived: “Just got a Rufous-eared Warbler!”

Rufous-eared Warbler at the New Holme Bird Ringing Course

We also had a Capped Wheatear!

Capped Wheatear at the New Holme Bird Ringing Course

Day 8 : Saturday 9 September

On Saturday morning, it was back to the waterhole for a sunrise start:

Waterhole at the New Holme Bird Ringing Course

The previous Sunday had been cool, with no breeze for the first few hours of the day. On Wednesday morning, it was frozen solid. But calm. Saturday morning was much warmer, but much breezier from early in the morning. With mist nets completely out in the open, we couldn’t expect to make a large catch. The objective of the morning was a big increase in the overall sample size of Grey-backed Sparrow-larks. We caught 20, and brought the total for the species to 130 birds. .

It turned out to be lark day!

Stark's Lark, New Holme Bird Ringing Course

Stark’s Lark!

Eastern Clapper Lark

Eastern Clapper Lark!! We caught two Eastern Clapper Larks and one Stark’s Lark.

Rare is common, and common is rare!

The rare species of which we catch only one or two individuals are fascinating. But it is the common species with large sample sizes that, from a science perspective, are the most valuable. These are the species that, ultimately, we can write papers about, that students can write up for their PhDs. Can we do anything with the measurement data on 130 Grey-backed Sparrow-larks, collected on three days (3rd, 6th and 9th September)? Look at Roberts 7 which summarizes all that is known about southern Africa’s birds. Discover that the measurements presented there are based on samples of only 12 females and 14 males. These sample sizes are too small to be considered reliable. So we have processed our 58 females and 72 males into a paper in Biodiversity Observations. The main results are that male Grey-backed Sparrow-larks are about 3% larger than females; sexual dimorphism in plumage is well-known, but dimorphism in size is apparently not.

A bit of a red herring, more or less!

In the process of writing the paper about Grey-backed Sparrow-larks, we had to look at earlier papers that contained relevant data. Here is part of the Methods section of one paper:

collecting specmines

To collect our data, we used mistnets to catch birds, we ringed them, measured them and then let them go free to carry on with life. This guy used a rifle and shotgun, and the birds ended up as study skins in a museum! Bear in mind that this fieldwork was done in 1965/66, nearly six decades ago, when mistnets were still in their infancy and the only way to get hold of birds to examine them close up was to shoot them. This diagram summaries the results obtained from shooting 57 Grey-backed Sparrow-larks:

Results, Grey-backed Sparrow-lark

The top and bottom panels we can do far better now, with much larger samples, using mistnets. The information in the second panel cannot be obtained by bird ringers! The quick and dirty way to discover the timing of the breeding season is to shoot birds, to dissect the males and to measure the length of the testes. They are only big in the breeding season; in this particular year, March, April and May. Flight is an energetically expensive activity. Birds save a lot of energy minimizing the size of the testes when they are not needed. Nowadays, the breeding season is found by watching behaviour and working out when the birds we are studying have nests.

The future and the past

Here is the list of ringing events for 2024.

And here is the list of blogs describing past BDI ringing events, going back to 2019.

Les Underhill
Les Underhill
Prof Les Underhill has been Director of the Animal Demography Unit (ADU) at the University of Cape Town since it started in 1991. Although citizen science in biology is Les’s passion, his academic background is in mathematical statistics. He was awarded his PhD in abstract multivariate analyses in 1973 at UCT and what he likes to say about his PhD is that he solved a problem that no one has ever had. He soon grasped that this was not the field to which he wanted to devote his life, so he retrained himself as an applied statistician, solving real-world problems.