Goldfinch Survey - Charming to Eat You!

I don't know about all of you, but a while ago I noticed that there seemed to be a lot more Goldfinch in the garden than I remember ever seeing before. After studying the Goldfinch closely, it was clear that they were mainly feeding on the sunflower heart feeders, and not even touching the nyger seeds or other food offerings in the garden.

So I persuaded my dad to let me get a large 12 port sunflower heart feeder so I could do my own garden Goldfinch study.  The feeder needs to be so big, as it will be the only sunflower heart feeder in the garden during the survey to ensure that I can accurately measure how much the Goldfinch are eating. I want to record the volume of food they are eating and compare this against the numbers of birds visiting, national Goldfinch number trends, temperature, weather conditions etc.

Once the 12 port feed arrived, I weighed out 100g of sunflower hearts and measured how much of the feeder this would fill, which then enabled me to draw a scale onto the feeder in permanent marker, making it easier record how much seed is being eaten every day.

On 22nd September, I started recording the results daily; volume of food eaten, weather, min temperature and max temperature.  I also tried feeding kibbled sunflower hearts as well as whole ones to see if that made any difference.

As I now have just over 6 weeks of data, I thought I would take a first look at the results.  The seed eaten on the chart below is all recorded in grams and the Goldfinch numbers are taken from the weekly results I record for the BTO's Garden Birdwatch Survey.  You can click on the chart to make it bigger and easier to read.

So here are some findings from the first 6 weeks:

1. Volume of food eaten. The Goldfinch have eaten a massive 32.2kg of sunflower hearts in just 6 weeks. So this is going to be quite an expensive survey, unless of course any kind bird food companies out there would like to sponsor the survey.

2. Waste! We all know what messy eaters Goldfinch are. From 22nd September until 3rd October, the feeder was hung in the tree and any waste was allowed to just fall on the floor and was not recorded. Even though I know a lot of seeds fall from the feeder, I was still amazed at just how much waste there was on the floor.

Tray attempt 1
The trays you can get with the feeders to catch the seeds really aren't big enough to catch the waste, and the seeds tend to just bounce off, especially on such a tall feeder.

Tray attempt 2
Next we tried cutting the bottom off a large gorilla bucket, leaving a rim round to stop seeds falling off.  This was attached to the feeder with wire, but it had a few problems, especially with portly Wood Pigeons. Every time they decided to perch on the edge, the rubber would bend and buckle and the seeds would fall out. Most mornings and evenings I would find the bucket tray almost vertical and doing no good at all.

Tray attempt 3
A proper fix needed to be put in place for the survey to work, so in the end I had a stainless steel tray made to catch any dropped seed. The tray has a large enough diameter (compared to the height of the feeder) to catch all the falling seed. It also has a big rim to prevent the fallen seeds blowing away. And of course it has drainage holes.

Any dropped seed can now be weighed at the end of each day and taken off the total of the amount of food gone from the feeder, which since 4th October has given much more accurate results for the volume of seed being eaten.  You can see the immediate impact of the new tray on the graph. On 4th October the volume of seed eaten dropped sharply as the waste could be weighed and taken off the volume of food taken from the feeder.

3. Peak! There was a big peak in Goldfinch numbers the week that started on 11th October. It will be interesting to see if this matches any surges in Goldfinch migration numbers.  I hope the BTO can help me with this.

4. Kibble. Goldfinch prefer a whole sunflower heart, they do not like them broken up. The bars in orange on the graph is when the broken up sunflower kibble was fed.  You can see how steeply the food eaten dropped during the kibble weeks. I am not sure, but does anyone know if the very core of a sunflower heat is more nutritious that the other part? The finches do seem to roll the seed round in their beaks, almost peeling off some of the seed.

5. Temperature. Because it has been so mild and relatively dry (apart from the last week or so) there are no clear trends showing up yet in relation to the weather, so hopefully, I will be able to report more on this in my next update.

6. Other birds. Of course this feeder is not exclusively used by the Goldfinch, but they are the main birds feeding on it and the other garden bird numbers are quite consistent, so they don't really impact the results too significantly.

7. 12 Ports. As there are just 12 ports, there is a limit to how many birds can feed at once, although the tray has allowed for more birds to feed on the fallen seeds. So I wonder if the volume of food eaten will reach a set level even if more and more Goldfinch come to feed once it starts getting colder. We will have to see.

8. Sprawk! Our Sparrowhawk has been a more frequent visitor as the Goldfinch numbers have gone up. They certainly are noisy visitors and I wonder if that is something that is attracting the attention of the Sparrowhawk. Again, I will see how this trend continues.  I also have another blog coming soon on my observations of the Sprawk's behaviour in the garden.

9. Hygiene. Finches are quite susceptible to diseases like trichomonosis, so I ensure that the feeder is cleaned and disinfected weekly to avoid any disease being spread from the feeder.

This post was just a quick introduction to the survey I am doing.  At the time of writing, our Goldfinch numbers have dropped off a little, but there is a lot more information to be collected over Winter. I will post the next set of results once we see a change in temperature.

If you are interested in tracking the Goldfinch numbers in your garden, the BTO are also doing a survey that you can take part in. You can find out more by clicking here.

Linking to Wild Bird Wednesday