Refreshment dip into Yzerfontein during lockdown

Kitch garden bird

At the beginning of May 2019, the quarter degree grid cell for Yzerfontein had 15 BirdPix records for 12 species. An expedition on 5 May 2019 changed that to 67 records of 39 species. There is a blog about this! During the remainder of 2019 and during the pandemic-dominated 2020, citizen scientists slowly improved these figures to 96 records of 45 species. At the start of 2021, South Africa was back in lockdown, a 6 am curfew meant that early morning starts were not feasible, and the beaches were closed. So on 9 January, it was time for a dip back into Yzerfontein to try to refresh as many species as feasible. It was time to honour the New Year’s resolution for Team Virtual Museum for citizen scientists …

… “Starting in my home grid cell on 1 January 2021, I will upload records to the Virtual Museum of as many species as possible (and I will be especially careful not to neglect the common species). Wherever I travel in 2021, I will do my best to keep the distribution maps up-to-date for as many species as possible” …

The edge of quarter degree grid cell 3318AC Yzerfontein is an hour from home. So with a 6 am start, I was at the intersection of the R27 and the R315 to this summer holiday resort by 7 am. See the map below …

Yzerfontein QDGC 3318AC

Underneath this map on the Virtual Museum website is the list of 45 species recorded so far. When I started, the bottom part of this list looked like this:

The end of the species list for the Yzerfontein QDGC before 9 January 2021

Here are species 34 to 45 on the list. The column that has 96 at the bottom tells us the number of BirdPix records for each species (and if you click on “Records” over on the right you get to see their details). The second last column gives the date of the most recent record for each species. So there are four records of Cape Sparrows, the most recent of which is on 12 December 2019.

Understanding the dates at the bottom of the column provides real insight into the up-to-dateness of the data for this grid cell. It is unusual for both the dates to be the same! This is how to calculate the top date of the two. Take the 45 “most recent” dates, and sort them. Pick the date in the middle: 5 May 2019. Half of the 45 species have been seen since this date and half before this date. For the bottom date, do the same process but with all 96 records. Half the records were made before 5 May 2019, and half of them since. This way of calculating the “date in the middle” produces a value called the “median” by statisticians. There is a blog about this!

After I got home, I submitted 50 records to BirdPix. Overnight, the members of the BirdPix expert panel have confirmed the IDs of all them. They are an awesome and dedicated group of people, and this is an important opportunity for us to express our thanks to them. The number of records for the grid cell has increased by 50 from 96 to 146. The number of species has grown by eight from from 45 to 53. Here is the list from House Sparrow to the end:

The end of the species list for the Yzerfontein QDGC after 9 January 2021

House Sparrow has shifted from being number 34 in the previous list to 39 now. In this part of the list, the new species are Southern Masked Weaver (47), African Sacred Ibis (51) and African Hoopoe (52). But the important thing to look at is how the median dates have changed. The median of the “last recorded dates” is now yesterday, 9 January 2021. That is because, when you sort these 53 dates, more than half the species were recorded on 9 January 2021! The bottom date has advanced from 5 May 2019 to 11 December 2019. Half of the 146 records were made before 11 December 2019, and half of them since. And that is of no concern!

The important thing is not the eight new species, but the fact that the median of the “last recorded dates” is right up-to-date. More than half the species were “refreshed“. The big challenge for 2021 is going to be to get this date into 2021 for as many grid cells as possible for as many projects as possible. Yzerfontein was easy; it only had 45 species.

Here are a few of the records from 9 January 2021:

African Hoopoe
In the Virtual Museum, this hoopoe is curated at http://vmus.adu.org.za/?vm=BirdPix-151655. This is the first record of the species in the grid cell for BirdPix

The hoopoe was on a lawn, in the dark shade under a tree. Considerately, it flew up onto a balcony and posed there. A chick is destined to receive a juicy worm.

Birds in flight are a challenge …

Black-shouldered Kite in flight
This Black-shouldered Kite can be found in the Virtual Museum at http://vmus.adu.org.za/?vm=BirdPix-151653

… but this Black-shouldered Kite hovered obligingly.

You will be pleased to know that this photo did not find its way into the Virtual Museum …

Kitch garden ornament

… the gull and the spurfowl seem oblivious to the kitsch garden ornament.

Law enforcement was prominently parked in the beach parking area, and no one was defying the lockdown regulations. There were lots of gulls on the beach, but the White-fronted Plovers had clearly not discovered that the beaches were deserted of humans, and they had congregated on the salt pan near the Strandkombuis.

White-fronted Plover on saltpan at Yzerfontein
Now you can see why it is called a White-fronted Plover! It was far away, and it was a dull morning. Look at the other photos curated at http://vmus.adu.org.za/?vm=BirdPix-151665!

You can find the complete BirdPix list of species for the Yzerfontein grid cell (and the map) by going to the link http://vmus.adu.org.za/vm_locus_map.php?vm=birdpix&locus=3318AC. (You can find the lists for other projects by changing “vm=birdpix” to other projects, eg “vm=reptilemap”, and you can change the code for the quarter degree grid cell).

So Yzerfontein is nicely refreshed for the birds. The dragonflies do however need attention (see http://vmus.adu.org.za/vm_locus_map.php?vm=odonatamap&locus=3318AC; the median date s in 2011!); there MUST be some freshwater somewhere in the grid cell. For LepiMAP, the median last record date is 1 February 2015 (see http://vmus.adu.org.za/vm_locus_map.php?vm=lepimap&locus=3318AC). But for ReptileMAP it is way back in 25 August 1983. Gosh, that is nearly four decades ago. Once the data starts to be this old on average, it ceases to be really valuable as current evidence of species distributions. That is the ultimate challenge.

This leads us back to our Virtual Museum resolution for 2021: “Keep the distribution maps up-to-date”. It is the commonest species in well-covered grid cells that are easy to neglect. And, at the same time, they are the easiest to keep up-to-date.

There are positives to having to leave after sunrise. Under normal circumstances, it would not have been light when I passed the huge Vissershok Landfill Site. A decade or so ago, this dump was well-known for hosting a some quite exotic storks: Marabou and Open-billed, and here is an amazing record from 2009 of White Storks at the dump. Yesterday, when it was still too early for a self-respecting, and presumably well-fed, White Stork to be up and about, the lamp posts at the nearby weighbridge where heavy trucks get examined were each occupied:

Grubby White Stork at Vissershok dump
Curated at http://vmus.adu.org.za/?vm=BirdPix-151593. This is only the third record of White Stork in the Bellville quarter degree grid cell 3318DC; to see the full list of bird species in BirdPix for this grid cell, go to http://vmus.adu.org.za/vm_locus_map.php?vm=birdpix&locus=3318DC

The moral of this story is that birds with white feathers should not feed in rubbish dumps.

But the moral of the blog is simple. Our anthem for 2021 is “refresh, refresh, refresh!”

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.

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