Little Tern – a species on the edge

This week’s blog is a guest blog and comes from local wildlife enthusiast and photographer, Ron Macdonald. It features intimate and breath-taking photos of the terns themselves, as well as Ron’s 40-plus years experience of the natural world and is a fascinating read.

Terns are my favourite seabirds and, of the four species that breed on Forvie NNR (Sandwich, Common, Arctic and Little), the Little tern is the one that tops my list. The bird’s good looks, its dainty flight and ability to pirouette mid-air to then dive headlong into the sea is very much part of my summer enjoyment at the Ythan estuary. I simply can’t get enough of watching & photographing them! In addition to being very photogenic, their behaviour is interesting to watch which I’ll try to illustrate in this blog. Finally, as suggested in the second part of the title, I’ll discuss why breeding numbers are trending downwards in Scotland and the efforts made at Forvie and elsewhere to halt the decline.

A Little Tern rising from the estuary after an unsuccessful dive

Little terns return from their West African wintering ground from mid-April onward and immediately start pairing up. The outer sand banks of the Ythan estuary, exposed at low tide, are where they gather and which I call their ‘courting club’. Typically, female birds await to be be courtship fed by the males or if they get impatient pursuing the males high up over the estuary to demand to be fed. Sometimes the female will take the fish offering from the male but then aggressively turn on him. I’ve also seen a courting pair joined by a third bird which I’ve taken to be a female bird ever hopeful of a free feed but that’s just conjecture.

Playing hard to get! A male tempts a prospective mate with a wee fishie but she’s not interested
A pair bond being cemented by the gift of a sand eel.
A female chasing the male high above the Ythan estuary
Or perhaps two competing males fighting?
A female demanding to be fed
And after being fed showing the male the door! Maybe it wasn’t her bonded mate? So many questions and so few answers!
I sometimes saw the terns performing elaborate moves as if they were dancing or in this case playing at leap-frog!
A pair displaying to each other
A Little tern displaying to its mate by making a heart shape out of water droplets. Honestly!

Two’s company, three’s a crowd. Two females vie for the gift of a sand eel. He doesn’t look as if he’s going to give it to either of them!

A female swallowing the sand eel provided by her mate
And the birds then mating
Little terns in a sand storm
Three Little terns and two Common terns in the midst of a sand storm raging across the estuary.

The Ups and mostly Downs of Breeding Little Terns in the UK

The long term UK trend for the Little tern is downward and nowadays its estimated that there are less than 2000 breeding pairs as shown in the graph below from the Joint Nature Conservation Committee’s (JNCC) Little tern species account. Between 1985 and 2000 there has been a long-term decline in the UK with little tern numbers down by 38%.  More recently between 2000 and 2015 the trend is -18%.

The Index of Abundance of the Little tern from 1986-2020 in the UK. Dotted lines show the 95% confidence limit. From the JNCC Little tern Species Report

The Scottish little tern population increased between Operation Seafarer (1968-1970) and the Seabird Colony Register (1969 -1998) but had fallen again by the Seabird 2000 census. The overall trend has been gradually decreasing since monitoring began and has remained below the baseline since 1989. However, as the confidence limits are wide, the trend should be interpreted with caution. In 2019, the index was 48% below the baseline (JNCC Little Tern Species report)

The Index of Abundance of the Little tern from 1986-2020 in Scotland. Dotted lines show the 95% confidence limits. Taken from the JNCC Little tern species account.

The trend at Forvie NNR, as shown in the table below, from 2007 to 2022 is somewhat different in that the maximum breeding pairs were present in 2013 and 2014, breeding seasons which produced good numbers of fledged young.

Year` Number of breeding pairs Number of young fledged

2007 20 1

2008 21 8

2009 37 73

2010 37 17

2011 31 34

2012 27 3

2013 40 42

2014 42 74

2015 19 0

2016 0 0

2017 5 0

2018 26 13

2019 28 0

2020 25 0

2021 25 2

2022 10 17

Key drivers affecting breeding success at Forvie NNR

Little terns prefer to nest in open or shingle beaches with little vegetation. They are often located below the Mean High Water Mean Spring (MHWS) tide limit so are prone to flooding during Spring tides. In addition, Little terns often nest on beaches popular with the public so disturbance by people and dogs can be significant without the areas being roped off and safeguarded by wardens to advise people of the risk to the birds.

At Forvie the Little terns breed on raised shingle terraces above MHWS so are safe from flooding. In addition, the area is closed to the general public from 1 April – 31 August thereby avoiding disturbance by visitors to the Reserve.

The principal threat at Forvie is predation by foxes and other bird species. To combat the threat by foxes the NatureScot Forvie team each year fence off a large area of shingle and low lying sandy areas which allows all four tern species and the large colony of Black-headed gulls to nest in relative safety. However foxes being foxes they do occasionally take some eggs and birds, probably from birds nesting outwith the fenced area.

A Red fox passing the fenced ternary on Forvie NNR with a young Black headed gull in its jaws. June 2022.

Whereas the fenced area is in the main effective against predation by foxes, aerial bird predators can and do access the ternery. For example from 2015 – 2017 and from 2019 -2020 there were no fledged young produced and the reason only came to light when footage from a camera trap revealed that oystercatchers nesting within the ternery were eating the Little tern eggs. It usually occurred when the terns performed dreads, lifting off en masse from the colony which allowed the Oystercatchers to nip in and eat the eggs before the terns returned

An oystercatcher about to eat a Little tern egg as captured by a NatureScot camera trap

In 2022 it was the turn of Black-headed gulls to predate the eggs. All first clutches of the Little terns that laid eggs were eaten by a Black-headed gull or gulls. Often it is the same individual Oystercatcher or Black headed gull that specialises in predating the eggs. Fortunately the Little terns relaid with 17 chicks fledged from 10 pairs. So what initially looked to be a fourth blank season in a row turned out to be a relatively successful one, much to the relief of the NatureScot staff who work so hard at safeguarding all four species of terns as well as the ,large colony of Black-headed gulls.

A newly hatched Little tern chick on Forvie NNR

What Future for the Little Tern in Scotland?

In June 2022 The National Lottery Heritage Fund awarded NatureScot £4.2 million funding for their Species on the Edge Project. The funding will support urgent action to help save 37 of Scotland’s most vulnerable coastal and island species, including Little tern. RSPB Scotland is leading efforts to protect and enhance the Little tern, concentrating early efforts on the small isolated Little tern colonies on the Scottish islands, engaging local communities to become involved in their long term protection.

On Forvie NNR, NatureScot staff have tried measures such as hand painted plaster cast models of Little terns to nest within the fenced area and tern shelters to provid protection for the chicks from avian predators. All these efforts have had limited, if any, success. The key is dissuading or preventing potential avian predators. NatureScot staff continue to explore ways to safeguard the colony from predation.