A Hunting Heron - Voles and Fish

Over the past several years I have been fortunate to see Grey Heron on many occasions. I have monitored a colony in Warwick and often see them at St. Nicholas Park and on my patch.

This morning I watched an individual Heron for some time as it hunted on the mill pond at the Saxon Mill. I watched as it stood stock still waiting for prey. It dived forward several times and failed each time, it got me thinking about what the Herons success rate was.

As I continued to watch a marveled at how controlled and stealthy such a large bird is. It places its feet carefully and lifts them to minimise splashes. It turns its head carefully watching multiple angles and once it detects a prey moves into position to start foraging.

The heron moved from the reeded central area where it was being unsuccessful to the bank side where over hanging trees might have improved visibility.

Whilst fishing here it saw something in the rocks on the bank side and quickly darted in to grab what seemed to be a vole. In the following sequence of photos you can see that it grabbed it with the tip of its beak and then rather than swallowing immediately it took it to the water and dipped it into the river. I do not think this was to drown the prey as it was too short a time but could have made swallowing easier as straight after it gulped the vole down.

The Heron grabs the vole side on from the rocks to the left

The Heron re-orientates the vole by gripping it by the head and neck

The Heron then dips the vole into the river

The Heron the swallows the vole whole, note the bulge in the neck as it passes down the crop.

Following this meal the Heron moved out of site under some low hanging branches. Here it spent 5 or 6 minutes before a splash could be heard and it emerged on the bank carrying a substantially sized Perch. Again the Heron did not immediately swallow its prey. Instead it moved swiftly away from the bank side and quickly flew across the river to thicker reeds where it then ate the fish. It was likely worried that another predator would try and steal his food and so relocated to better cover in order to keep it.

Interested by the herons feeding habits I found a paper in Bird Study which looked at how successful herons could be. The article indicated a basic frequency of prey at 1 per 55 mins with a 50% success rate.

I reckon I watched the heron for about 20 minutes and estimated it also to have a 50% success rate but a frequency of 1 per 12.5 mins.

Bushnell Aggressor Trophy Cam HD Review

Only strangers to this blog will not know of my long-term camera trapping study. As of tomorrow, it will enter its 4th year of continuous operation. To start this I decided to upgrade the camera I have been using as my main camera. In the past year, I have experimented with Acorn models and whilst I have been impressed by them I opted once more for a Bushnell as my main camera. I did this mainly because I have been so impressed by the long-term stability that Bushnell has offered in the past.

My older Bushnell Trophy Cam ran 24 hours a day 7 days a week for 3 years with very few problems. I decided to upgrade for two reasons:

1. I wanted ti to improve the image quality I am getting

2. I was starting to get a concurrent error in which the camera would multiple trigger resulting in large volumes of clips to go through,

After a little research, I opted for the Bushnell Aggressor Trophy HD that I purchased from NHBS

Features

F2.8 Lens with a 38 degree of field of view
IR- Flash
Display Screen
SDHC Card
Hyper PIR
0.25s Photo response time
1s Video response time
Powered by 8 AA batteries

So how does it respond? well, so far I m impressed. It has been out for 6 days and the footage is clear. I have two clips to show this.

As I continue to use the camera I will continue to comment, especially as I think the field of view is different and I will need to reposition the camera to get the best footage.

Data collected over the past three years will be analysed and the results filtered into the blog as and when I finish it.

A new species for my patch

Whilst out for drinks on Friday evening the first thing I spotted as I took my seat beside the mill pond was a species of bird I had never seen at the Saxon Mill before - a Little Egret.

This small heron is becoming increasingly common in the UK. I can remember being amazed at seeing them on the Hayle Estuary in the mid-1990's when they were a national rarity today they are a breeding species found across the country, They often nest alongside Herons in colonies. I have seen them before at Warwick Castle Park and also at Aylesford School but this was first for the mill.

They are elegant birds with startlingly golden yellow feet. I took this on Saturday when the bird was still present, it was gone by Sunday.

A Teal at Last

Today I finally got a good shot of a teal. I am a little surprised that a pair of drake Teal are still present on the river but today the lighting was good and I was able to gain their trust.

I spotted the Teal some distance away, luckily it was on the other bankside allowing me to get closer to it. It is remarkable how such a striking bird can be so hard to see. Just look at the picture below, how long does it take you to spot the Teal.

As I approached I could see that he was aware of me and was preparing to fly. I paused and sat on the bank. I avoided looking directly at him, such direct eye contact can spook birds and animals. I sat for a good five minutes keeping him in my peripheral vision. Eventually, he settled down and then began to feed, finally, it moved out of cover and allowed me to get the shots I wanted. It's a reminder that wildlife is just as much about patience as it is about luck and skill.

As I left I noticed a pair of Buzzards, one had been about all morning but a second had now appeared and the two began to circle. I saw them swoop together and wondered if it was a mating ritual, however, on a second pass it seemed more aggressive. I got a quick shot off and noted that one of the individuals moved off quickly following the final pass, a piece of behaviour called 'taloning' where an approaching Buzzard will reach out with its legs and talons and the other will turn and flip to bear its own talons.

In raptor's this is often used in food passing where one adult will pass food to another often a male to a female either as a courtship gift or a to feed a nesting female.

In other news, expect updates on two areas. Its the time of year for nesting and I have preliminary survey information on breeding swans in the area. At the moment I have located 3 nests but more news in a separate post soon.

The second news is in relation to my camera trapping. The main camera has been operating for three years and I have just purchased an upgrade for it. When it arrives I will do a review. Secondly, I have abandoned river cam. It's had some success but is limited. I have found a burrow with interesting promise and I have relocated that camera there. More information soon about who is living there.