29 May 2015

The Data Pond

I've been camera trapping on a small farm just outside the town of Paarl (which is situated very close to Cape Town) from January to April this year.

Bushnell camera trap at the farm's pond

The camera trap at the small farm pond in the photograph above got some interesting results. The initial camera trap positioning was fairly good and I got a Cape Grysbok and Water Mongoose early on.

Cape Grysbok (Kaapse Grysbok - Raphicerus melanotis) getting a drink

However the mongoose decided that my camera placement could do with some adjustment.

Marsh Mongoose (Kommetjiegatmuishond - Atilax paludinosus) freelance camera trap adjuster

After the adjustment I didn't get a decent photograph of any more mammals, but the camera did focus on a small part of the bank and as a result captured many photographs of the resident water birds.

Black-Crowned Night Heron (Gewone Nagreier - Nycticorax nycticorax) sneaking past the camera

Many of the photographs had multiple species visible at once and as a result it took a while to capture the data. In the end I recorded 325 observations over the 3 week period. This is a sizable amount, and I was curious whether the reporting feature I recently added to WildLog might show some interesting trends.

First up is a chart showing the number of observations recorded compared to the duration of the observation (using 30 second intervals). The shape of the curve is fairly standard, with a very large amount of very short observations followed by a sharp drop. What I find interesting is that there is a high number of observations extending past 30 seconds and into the 3-4 minute mark. Clearly these water birds at the pond spend more time feeding in a small area, before moving on, compared to more conventional camera trap subjects and locations.

Another benefit of getting such a high number of observations over suck a short period of time is that you can compare the exact time the observations were made too each other, without having to worry too much about the change in season, sunrise, etc. In this case the data shows a huge spike in activity between 5:30am and 8:30am.

Looking at the bar chart that maps each time to a relative time of day category (based on season and sunrise) the same trend is visible. Sunrise and early morning is clearly the peek of activity at the pond.

The last chart I want to put in this blog post is one showing the number of observations recorded during each 24 hour period. Looking at the chart it seems like there might be a possible pattern: days with high activity are usually followed by days of low activity. I'm assuming this can be attributed to the birds' feeding behaviour. These species will be mostly feeding on plants, small animals, insect, invertebrates, etc. and it makes sense to allow the prey species some time to recover before feeding again in the same area.

Another interesting observation is that the birds would often feed together. There are many benefits to doing so, ranging from better protection from predators, to the fact that the disturbance caused by one bird feeding might make things easier for the other bird to catch its prey. The different species usually don't compete directly with each other for the same food.

The animated GIF below is somewhat on the large size (about 8 MB), but I'm going to try and include it in this blog post because I think it helps to illustrate life at the pond very well. The following species can be seen in the clip:
  • Yellow-Billed Duck (Geelbekeend - Anas undulata)
  • Common Moorhen (Grootwaterhoender - Gallinula chloropus)
  • Cape Wagtail (Gewone Kwikkie - Motacilla capensis)
  • Cape Weaver (Kaapse Wewer - Ploceus capensis)
  • Black Crake (Swartriethaan - Amaurornis flavirostra)
  • Little Grebe (Kleindobbertjie - Tachybaptus ruficollis)

About 20 minutes of bird activity at the pond condensed into a few seconds

For those wondering, in total this set recorded 19 species. The 6 species mentioned above was by far the most numerous visitors.

During my camera trapping excursions I came across a dead Yellow-Billed Duck and was able to get some close-up photos.

Close-up of the wings of a dead Yellow-Billed Duck

The Yellow-Billed Duck is a type of Dabbling Duck and has the grooves along the edge of the bill to help with feeding.

The duck's bill

I'm really enjoying the new reporting tools in WildLog. Even though these findings are nothing strange or ground-breaking I still learn a lot (first hand) from them. It is fun to see the data take shape after going through the hard work of capturing it.