Month: February 2016

Starling Murmurations

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Each winter for the last few years, there have been starling murmurations over Grantham and this year is no exception! I saw them gathering on a pylon in the fields beside Harlaxton as I drove along the A607 in this evening, and as I drove past they all rose en mass and began to flock over the western tip of Grantham. I parked up for a few moments to watch this incredible spectacle of aerial gymnastics.

There are several theories as to why starlings flock together like this and treat us to such a display. They gather just before roosting, which they do communally, and so you see smaller flocks gradually join the largest flock so that the numbers grow and grow before they drop down to the trees and shrubs where they spend the night communally. This grouping together may allow them to exchange information on good feeding spots, or just help them to gather with the rest of the local starlings to maximise the warmth which multiple bodies brings on cold winter nights.

The birds move in unison, twisting and turning in shapes a little like those you’d see in a lava lamp, and this behaviour increases in speed and complexity if there is a predator about. This is believed to be another of the reasons for the murmuration behaviour. Safety in numbers is an instinctive behaviour for many species – including birds, fish and mammals – and it works on the basis that if you are in a large crowd, there are many targets beside yourself which makes it unlikely that a predator will get you individually. The dynamic flight patterns of the murmuration adds a further element of safety by confusing the predator as the flock bends, twists and turns as one.

Starlings are a common sight, but they are actually a red list species. Each bird in the UK is given a colour-coded assessment based on the current status of the species. This works on the traffic light system – green indicates least conservation concern whilst red indicates the highest conservation priority. Starlings are on the red list because, despite these large winter flocks appearing impressive, long-term monitoring by the British Trust for Ornithology shows that starling numbers have fallen to just 1/3 of their population in the mid-1970’s. If this decline were to continue along the current trend, then it would be only a short time before starlings were all but extinct.

The flocks will begin to disperse as starlings pair up and establish nests, so take the opportunity to watch this natural phenomena whilst you have the chance! The hour before sunset is the best time to get out and look for them, and they are currently focused on the western tip of Grantham, sometimes moving over the centre earlier in the evening.

If you’re looking to commision ornithological surveys such as wintering bird surveys in the midlands, check out Landscape Science Consultancy’s website here.

Hazel flowers

Grantham Ecology3 Comments

The arrival of hazel flowers is one of my favourite sights of spring – in amongst the bare hedgerows, there is something magical about finding a hazel heavy with catkins, as though somebody had been out and hung decorations upon a bare tree in the middle of nowhere.

A tiny female hazel flower in the foreground with the male hazel catkins - an inflorescence containing an average of 240 individual flowers - in the background.
A tiny female hazel flower in the foreground with the male hazel catkins – an inflorescence containing an average of 240 individual flowers – in the background.

The hazel has both male and female flowers on each shrub, and the two flowers are quite different. The male flowers are gathered within the long, breeze-blown catkins and these are by far the most prominent. Each catkin is made up of many individual flowers – these are the small green/yellow male flowers which produce the pollen. There are around 240 male flowers in each catkin and they form during the previous summer so that they are ready to open in the dead of winter and flower through the spring.

The hazel is wind pollinated and the pollen from the catkins blows to reach the female flowers which you would never spot unless you looked carefully – they are tiny individual flowers, visible only as red styles protruding from a green bud-like structure on the same branches as the male flowers.

A female hazel flower - the tiny red styles can be seen protruding from the green bud-like structure on the branch. The styles are each just a few milimetres long so you need to look closely to spot them amongst the catkins!
A female hazel flower – the tiny red styles can be seen protruding from the green bud-like structure on the branch. The styles are each just a few milimetres long so you need to look closely to spot them amongst the catkins!

Hazels typically begin flowering in January and will go on into April, although there were open flowers in December this winter. Once pollinated in the springtime, the female flowers set to work producing the hazelnuts which ripen in the autumn.

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A hazel nut – the eventual result of the pollination of the tiny female flowers with pollen from the male catkins. This photo taken at the end of August before the nuts are yet fully ripe.

Hazel flowers are an important source of pollen for bees, especially those individuals which have overwintered and emerge early when there is little alternative pollen available. Bees collect pollen in medium sized pellets as it is a source of fats and proteins. This is distinct from their need for nectar which is a sugary food source to provide energy and allow production of honey.

A close-up shot of the many male flowers which each make up a hazel catkin. It is these flowers which produce the pollen gathered by bees in the early springtime.
A close-up shot of the many male flowers which each make up a hazel catkin. It is these flowers which produce the pollen gathered by bees in the early springtime.

Hazels are wind pollinated and do not therefore require bees for pollination, although it is noticeable that the female styles are pigmented which may indicate an attractive function. A paper by Pietrowska mentions that the bracts of hazel are adapted for pollen retention. This means that the pollen collects when it leaves the male flowers rather than scattering immediately to the wind – this benefits wind dispersal but also facilitates the collection of pollen by bees. Perhaps the red pigmentation of the yellow flowers is a trick to entice bees  into making the occasional visit to a red female flower, in the hope that nectar may be available, and therefore supplementing the primary wind pollination strategy?

A hazel in the Cotswolds in full flower in January 2015.
A hazel in full flower in January 2015.