A Smelly Old Business

How do birds navigate over long distances? This complex question has been the subject of debate and controversy among scientists for decades, with Earth's magnetic field and the birds’ own sense of smell among the factors said to play a part.

It’s a subject discussed previously on Another Bird Blog but here's an interesting update by way of scientific experiments on an island I know very well.

In new investigations researchers closely followed the movements and behaviour of 32 Scopoli's Shearwaters Calonectris diomedea off the coast of Menorca. 

Scopoli's Shearwaters breed across the Mediterranean on Menorca, Ibiza, Formentera, Cabrera, Conillera and Dragonera. The majority of the population of Scopoli's Shearwater spend the non-breeding season in the Atlantic, including areas off the west coast of Africa and east coast of Brazil. They return to the Mediterranean in spring where they breed on rocky coasts and offshore islands, often close to or alongside Balearic Shearwaters Puffinus mauretanicus.  Hence, I see both species of shearwater when I visit Menorca in early May each year and when both are clearly visible from the shore, numbers varying with the daily weather conditions.

 Scopoli's Shearwater  - Daniele Occhiatto

Baearic Shearwater -Marcabrera [CC BY-SA 2.0], via Wikimedia Commons 

Menorca

Now, researchers from the universities of Oxford, Barcelona and Pisa have shown in a new experiment that the sense of smell (olfaction) is almost certainly a key factor in long-distance oceanic navigation, eliminating previous misgivings about this hypothesis. 

For the experiment the birds were split into three groups: one made temporarily anosmic (unable to smell) through nasal irrigation with zinc sulphate; another carrying small magnets; and a control group. Miniature GPS loggers were attached to the birds as they nested and incubated eggs in crevices and caves on the rocky Menorcan coast. But rather than being displaced, they were then tracked as they engaged in natural foraging trips. 

Study leader Oliver Padget, a doctoral candidate in Oxford University's Department of Zoology, said: "Navigation over the ocean is probably the extreme challenge for birds, given the long distances covered, the changing environment, and the lack of stable landmarks. Previous experiments have focused on the physical displacement of birds, combined with some form of sensory manipulation such as magnetic or olfactory deprivation. Evidence from these experiments has suggested that removing a bird's sense of smell impairs homing, whereas disruption of the magnetic sense has yielded inconclusive results"

"However, critics have questioned whether birds would behave in the same way had they not been artificially displaced, as well as arguing that rather than affecting a bird's ability to navigate, sensory deprivation may in fact impair a related function, such as its motivation to return home or its ability to forage. Our new study eliminates these objections, meaning it will be very difficult in future to argue that olfaction is not involved in long-distance oceanic navigation in birds."

All birds went out on foraging trips as normal, gained weight through successful foraging, and returned to exchange incubation periods with their partners. Thus, removing a bird's sense of smell does not appear to impair either its motivation to return home or its ability to forage effectively. However, although the anosmic birds made successful trips to the Catalan coast and other distant foraging grounds, they showed significantly different orientation behaviour from the controls during the at-sea stage of their return journeys. 

Scopoli's Shearwater - Martin Garner

Instead of being well-oriented towards home when they were out of sight of land, they embarked on curiously straight but poorly oriented flights across the ocean, as if following a compass bearing away from the foraging grounds without being able to update their position. Their orientation then improved when approaching land, suggesting that birds must consult an olfactory map when out of sight of land but are subsequently able to find home using familiar landscape features. 

Senior author Tim Guilford said: "To the best of our knowledge, this is the first study that follows free-ranging foraging trips in sensorily manipulated birds. The displacement experiment has rightly been at the heart of bird navigation studies and has produced powerful findings on what birds are able to do in the absence of information collected on their outward journey. But by its nature, the displacement experiment cannot tell us what birds would do if they had the option of using outward-journey information, as they did in our study. This heralds a whole new era of work in which careful track analysis of free-ranging movements, with and without experimental interventions, can provide inferences about the underlying behavioural mechanisms of navigation. Precision on-board tracking technology and new analytical methods, too computationally heavy to have been possible in the past have made this feasible."

Story Source: University of Oxford. "Sense of smell is key factor in bird navigation, new study shows." Science Daily, 29 August 2017.

Linking today to Stewart's World Bird Wednesday.

Change Of Plan

The forecast for Wednesday was decidedly “dodgy” but with it being the best for several days ahead, we decided to chance a ringing session up at Barnacre. The problem was when I got up at 0530 and looked out of the window the trees were wafting around so I sent Andy a text and said I’d go birding instead. 

I was early so stopped at Pilling Lane Ends to count the Little Egrets at the roost. Thirty-five was my total but I suspect many were hidden from view in this so called “amenity area” that is now just a neglected wilderness. 

At Braides Farm - 80+ Curlews and a roosting Buzzard. 

At Conder green Once again Lapwings proved the most numerous bird with at least 240 scattered around the site, on the island, the grassland and in the tidal creeks. Other waders were few and far between with just handfuls of Curlew, Redshank, and a single Common Sandpiper. Fishing the pool was a single Goosander, 4 Cormorant and 4 Little Egret. Two Little Grebe have moved to the creeks where I also found 8 Teal. 

Lapwing

Little Egret

It was on a circuit of Jeremy Lane that I stopped to look through a flock of 600-800 Black-headed Gulls. Almost on cue I found an adult Mediterranean Gull I had hoped to see. There have been lots of “med gulls” sighted along the coast in recent weeks and the best way to find one by searching through flocks of Black-headed Gulls. While it’s nice to see one, the “med gull” is no longer a rarity. 

Mediterranean Gull - adult winter by M. Jackson, Mull Birds

The Mediterranean Gull is the most recent addition to the species of seabirds breeding in the UK. By 2010, there were over 600-700 nesting pairs, mostly on the south and south-east coasts of England. 

The range of the Mediterranean Gull expanded markedly over the last 50 years. A westward expansion started in Hungary, where it was breeding regularly by 1953, then into Germany and Belgium during the 1960s and the Netherlands by 1970. Range expansion also occurred in an eastward direction during the 1970s and 1980s. The first breeding occurrence in Britain was in 1968, at Needs Ore Point (Hampshire). Thereafter, a pair bred at Dungeness (Kent), in 1979, increasing to two pairs by 1985. A site in north Kent was colonised in 1983, which later became established as one of the major colonies in England. Also during this period, a handful of other breeding attempts were made, including pairings with Black-headed Gulls.  

I wasn’t finding much around Jeremy Lane until I stopped to watch a Kestrel hovering over the footpath at Cockersands. There was a Marsh Harrier again, this one hunting the fields behind the old abbey, seen off in turn by Carrion Crows and Lapwings. After a while the harrier did a disappearing act, something they are good at for such a large bird. 

Marsh Harrier and Lapwings

I stopped at Gulf Lane where I dropped seed at the Linnet field and did a spot count for the week of about 100 finches - 50/50 Linnet/Goldfinch again. The weather forecast for the week ahead, wind above 15mph every day, will put paid to plans to ring any time soon. A couple of Stock Doves have found our food drop. 

Stock Dove

I was on the way to Knott End to grab some shopping but stopped along the promenade to watch the incoming tide. Recent days have seen good numbers of Sandwich Terns roosting on the sands at high tide, migrant terns that feed in Morecambe Bay while passing through the area on their way south to winter off West Africa. My minimum count was 250 with many roosting for a short period and then as the tide arrived, flying off over the jetty, south-west and up the River Wyre. 

Sandwich Terns

Sandwich Terns

 Sandwich Tern

Sandwich Tern - Range by CC BY-SA 3.0 Wiki 

Knott End Ferry

 Back soon with more birds on Another Bird Blog.  In the meantime I'm linking to Eileen's Saturday Blog.

Some You Win

The weatherman kindly told us that Thursday 31st August was the Meteorological End of Summer. I tried to recall more than a handful of summery days during of May, June, July and August that resembled summer but I quickly gave up. 

Friday 1st September. I took a flying visit to Conder Green where a distant Kingfisher proved the only bird of note as it dived into the now shallow water from the top of the marker post. Otherwise there was the usual fare – An increase to 17 Teal, 9 Little Grebe, 80 Lapwing, 5 Snipe, 1 Goosander and 1 Common Sandpiper. The female Tufted Duck is reduced to just three youngsters now. A few pairs of Tufted Ducks have bred on the pool for the last three years but always struggle to get more than one or two youngsters up to full size. 

Kingfisher

Tufted Duck

I was on the way to Gulf Lane to unload a bucket of rape seed into our net ride in preparation for a ringing session on Saturday. The seed is back-up to the natural food that the 300+ Linnets and Goldfinch now target because those large numbers of birds will soon make a large dent in natural food availability. 

Saturday 2nd September dawned misty but bright with the promise of sun and little wind for our ringing. I met up with Andy at 0630 just as the sun rose over to the East. 

Pilling sunrise

Looking West at Pilling

Unfortunately the Linnets didn’t perform as well as have come to expect and we ended up with a meagre catch of just five birds, a total quite unlike our catches to date this autumn.  Howver, all is not lost as those five bring us to 150 newly ringed Linnets so far this autumn.

Linnet

The composition of the flock has changed considerably this week with now something like 50/50 Linnet/Goldfinch and just 200 birds in total this morning. Given the natural abundance of food at this time of year, both on site here and in the local area, the birds have many choices of where to feed. Additionally, the preferred feeding patch on site is some way from our single 80ft cut through the crop. 

We have seen a Sparrowhawk on at least three recent spot visits which leads us to think the hawk is a very regular visitor and may be deterring the finches from their usual habits. As Sparrowhawks are liable to do, once they find a reliable source of food, they come back time and time again. The hawk made two visits today, once trying to snatch a Linnet in the air and then later, moving along the fence line from where it could wait to pounce. The hawk flew off when I walked along the road towards its lookout post. 

Sparrowhawk

 

Some you win, some you lose and it won't stop us trying again soon.

We may not have had the biggest catch of the year but it was certainly good to be out in the sun for a change. 

Linking today to Stewart's World Bird Wednesday.

Never The Same

The alarm clock buzzed at 0520. I was due to meet Andy and Bryan at 0630 for another ringing session near Oakenclough. The weather forecast of a 2mph wind with no rain proved to be accurate and we enjoyed an eventful morning of both ringing and birding. Three pairs of eyes and ears proved extremely useful during the usual lulls in ringing. 

After an initial round of Great Tits, Coal Tits, a Blue Tit and just a single Willow Warbler it seemed as if the session might be below par for this always productive site. But within an hour the species changed when visible migration began, and after five hours we had caught 51 birds of 10 species. 

While no two ringing sessions are ever the same it was finches top of the leader board again with yet more Goldfinch and Lesser Redpoll. We had handfuls of both Willow Warbler and Chiffchaff together with another Tree Pipit. 

Totals - 14 Goldfinch, 8 Lesser Redpoll, 6 Willow Warbler, 5 Goldcrest, 4 Chiffchaff, 4 Chaffinch, 4 Coal Tit, 3 Great Tit, 1 Long-tailed Tit, 1 Blue Tit and 1 Tree Pipit. 

Willow Warbler

Long-tailed Tit

 

The Ringing Office

Lesser Redpoll

Tree Pipit

Birding proved very interesting and began with our second Osprey of the week. This one followed a similar route to the one on Friday last by flying North to South alongside Harris End Fell before disappearing from view. Seven Grey Herons appeared together from the south, circled for a while before they lost height and dropped to the north and towards the fisheries near Scorton. 

Other raptors seen – 2 Sparrowhawk,1 Kestrel and 9 Buzzard. The Buzzards appeared late in the morning as a “kettle” of 7 plus 2. Three Ravens added to the action on high. 

We noted a steady stream of high-flying hirundines with Swallows to the fore. 60+ Goldfinch and 30+ Chaffinch dominated the arriving finches where Lesser Redpolls seemed less vocal than normal. We were a little surprised to catch nine redpolls when so few seemed to be around. 

An initial count of 5 or 6 Mistle Thrushes turned into a massive 29 when two parties that arrived unseen at the North West corner of the site took to the sky flying east. As the thrushes spread out we counted a flock of 22 and then a gang of 7, all heading the same way. 

It’s often in September that people mistakenly report Fieldfares arriving early in the UK, when in fact Fieldfares do not really arrive here from Scandinavia until late September/October. What those observers have actually seen is a far less common but not unknown flock of Mistle Thrushes. Just last week a local birder, Bryan Yorke saw over 80 Mistle Thrushes in the hills north of Lancaster. 

Mistle Thrush

Seems like our largest UK thrush has enjoyed a good breeding season! 

Other birds noted in the plantation – a single Nuthatch and 2 or more Bullfinch.

Linking today to Eileen's Saturday.

Visit 4

Saturday was Visit 4 to our Project Linnet 2017/2018. With darker mornings and the evenings drawing in we make a slightly later start; fifteen minutes a week is the rule until the Autumn solstice. 

I met up with Andy at Gulf Lane at 0630 and even then we waited a while for the first Linnets to arrive. Our three previous August visits realised catches of 49, 37 and 43 Linnets respectively with not a single recapture from this year or the last. Such a huge turnover of birds for one small area! 

Although we counted circa 300 birds in the air at any one time today, not all were Linnets. The Linnets had been joined through the week by a flock of some 60+ Goldfinches. The Goldfinches had found their own niche by exploiting in particular a plant that resembled a tall dandelion but which may be sow thistle. The heads of the plant are stuffed with tiny black seeds, spot on for the species' fine ppointy bill. Meanwhile the Linnets preferred to feed out of sight, on the ground and on seed dropped by the maturing plants.

Sow Thistle?

Goldfinch food

 

Goldfinch on Common Thistle

After a number of guesses we concluded the huge flock to be split approximately 250+ Linnet and 50+ Goldfinch, the flocks now concentrating on the abundance of natural foods and relying less on our dried rape seed from a sack. However we did catch more Linnets, plus our first Goldfinch, in total 16 Linnet and 4 Goldfinch. 

Naturally enough our catch was dominated again by juveniles/first year birds, all four Goldfinch and 12 of the 16 Linnets. All of the Goldfinches we catch at this time of the year appear to be third broods, whereas the young Linnets we catch are definitely some weeks older and most part way through their post-juvenile moult. 

Goldfinch

Linnet

Part of the UK’s Goldfinch’s success story of recent years is down to its ability to exploit a wide range of nesting and feeding opportunities in orchards, hedgerows, open cultivated land, woodland edge, and perhaps crucially in recent years, gardens and suburban tree-lined streets. 

In contrast, the less adventurous Linnet population may be held back and in decline due to its dependence on gorse, rough uncultivated land and the traditional farmland habitat of the UK. Linnets are rarely found in gardens and orchards whereas the Goldfinch is now the most common bird in many gardens, especially where food is offered. 

Linnet

Other birds seen today - 1 Peregrine, 1 Buzzard, 1 Kestrel, 40+ Swallow, 2 Stock Dove, 3 Little Egret, 100+ Greylag Goose. 

Buzzard

Back soon with more news and views. 

First Vis Mig

I’d met up with Andy at Oakenclough at 0630 for a ringing session. All started fairly quiet and uneventful but as the minutes ticked by it became clear that the morning would see the first substantial visible migration of the autumn. 

An early highlight was the Osprey that powered in over the trees from the North West about 8am and then turned as if to plunge for a trout in the reservoir. It hovered briefly but then turned again and continued on a southerly track and out of sight to leave the trout for the Cormorants and anglers. 

There were plenty of other birds heading south, mainly finches and Swallows, but also 2 Song Thrush. After five hours we had counted 95+ Goldfinch, 45+ Lesser Redpoll, 30+ Chaffinch, 4+ Siskin and 4+ Tree Pipits arriving from the north and heading either into or over our ringing site. 

Our catch of 47 birds reflected the species we’d seen plus a few warblers that linger on site and the inevitable tit species of woodland habitat. Totals - 19 Goldfinch, 14 Lesser Redpoll, 4 Blue Tit, 2 Chaffinch, 2 Tree Pipit, 1 Chiffchaff, 1 Willow Warbler, 1 Wren, 1 Coal Tit, 1 Great Tit and 1 Goldcrest. 

Every single one of the Lesser Redpolls proved to be a recent juvenile, so young in fact that we considered most to be at least second broods, possibly third. Likewise the Goldfinches caught. None of the Lesser Redpolls could be sexed and all but two of the brown-headed Goldfinches were left unsexed. 

Lesser Redpoll

Lesser Redpoll

Goldfinch

Chaffinch

We missed a third Tree Pipit when one climbed out of the mist net before Andy could reach it. 

Tree Pipit

On the way home I clocked 2 Buzzard, 15 Pied Wagtails and good numbers of Swallows. At one farm I slowed to see a young Sparrowhawk try to take a Swallow in flight. The Swallow won by easily outmanoeuvring the inexperienced hawk. 

The forecast looks OK for Saturday with a wind speed of less than 10mph. If so we’re heading for Gulf Lane and a catch of more Linnets as part of Project Linnet 2017/2018.

Linking today with Eileen's Blog.

Cream Top Etc.

Conder Green was quiet as quiet can be this morning. I was a little late as I waited for the rain to stop, but even so, rarely have I seen the water and the immediate area so devoid of birds. There was a solitary Lapwing on the island and the usual handfuls of Cormorant, Little Grebe and Little Egret, but no sign of the regular Kingfisher. 

A dozen or so Pied Wagtails skittered around the margins, joined briefly by two loudly calling Green Sandpipers. The sandpipers flew off towards the canal and in the direction of Glasson Marsh.

Cormorant

Little Egret

I followed the Green Sandpipers and stopped overlooking Glasson Marsh where I hoped to see a Marsh Harrier. There have been good numbers about in recent weeks and one of my contacts tells me that a pair bred successfully in The Fylde. That’s the River Lune on the horizon. 

Glasson Marsh

Out on the marsh I could see a couple of Little Egret and Grey Heron, 2 Ravens, a Kestrel and a gang of about 30 Swallows. I found many Lapwings in the fields adjoining Jeremy Lane with upwards of 600 where the pastures are still sopping wet after the rain of recent weeks. One field had 5 Stock Dove as well as wagtails, gulls galore and a Grey Heron. 

I was side-tracked by a large bird flying inland, a Marsh Harrier. It stayed very distant as Marsh Harriers tend to do. As strong and fast flyers they have a knack of avoiding roads and people as the two pictures long-range of the female “cream top” show. For almost an hour the harrier stayed distant or completely out of sight and I think that at some point it flew out to Cockerham Marsh. 

Marsh Harrier

Marsh Harrier

The Marsh Harrier is typically illustrated in field guides as a sexually dimorphic species, with several age classes identifiable by differences in plumage pattern and colour. In some populations however it is known that the species can show extreme plumage variability in adult males and, to a lesser extent, in adult females. Populations may be markedly polymorphic with highly distinct patterns of coloration and almost continuous individual variation between those different morphs with few adult males resembling a typical ‘field-guide male’. Since this plumage variability is independent of age and sex, it is almost impossible to age birds solely from their plumage. This contradicts the established view and questions the claims of birders who age and sex Marsh Harriers from hundreds of yards away. 

Marsh Harriers are a still scarce, possibly declining breeder in Britain with just a few dots on the map in comparison to Europe. Their UK stronghold is East Anglia with a few pairs in NW England and others in locations withheld. 

Western Marsh Harrier - Circus aeruginosus 

At home Goldfinches are back in the garden with a good number appearing to be recently fledged youngsters. Goldfinches have been absent for weeks now as they feed on the plentiful seeds in the countryside. I will catch and ring some very soon. Last evening a young hedgehog paid us a visit. 

As with most small mammals living around humans, vehicles pose a great threat to hedgehogs. Many are run over as they attempt to cross roadways. It is suggested that peaks in road deaths are related to the breeding season and dispersal/exploration following independence. 

Hedgehog

From Wiki – “In 2006, McDonald's changed the design of their McFlurry containers to be more hedgehog-friendly. Previously hedgehogs would get their heads stuck in the container as they tried to lick the remaining food from inside the cup. Then being unable to get out, they would starve to death.” 

McDonald’s have a lot to answer for.  I went there once.

Linking today with Anni's Birding Blog.

Linnet Tales

Start time 0615. At last, a 4mph negligible wind and no rain. I met Andy at Pilling and we set a couple of single panel nets in time for Linnets to arrive from their overnight haunts and head for the seed plot. 

Within 15 minutes we had our first catch. We went on to a total of 43 new Linnets with zero recaptures from previous occasions. Of the 43 ringed we had 5 adult males and 38 juvenile/first years, broken down further to 20 males and 18 females. This brought our overall total to 129 Linnets ringed in August, an excellent start to Project Linnet 2017/18. 

Our maximum count of the flocks and smaller groups in attendance today was of approximately 200 Linnets at about 0930. The flock is almost entirely Linnets with just a handful of Goldfinches tagging along. 

Linnet

 

Linnet

Readers of a certain age will certainly remember a ditty featuring the Linnet and made famous by Cockney (London) music-hall in the early part of the 20th Century. “My old man said "Foller the van, and don't dilly dally on the way", the story of a couple doing a “moonlight flit” from their house in the dark of the night to avoid paying rent owed to the landlord. Anyone who knows the song will remember how the wife continues the story in the Cockney dialect -“Orf went the van wiv me 'ome packed in it, I followed on wiv me old cock linnet. 

The “old cock linnet” was the family pet – a linnet, a finch highly prized for its rich musical song a century and more ago. Around that period it has been estimated that 50% of households in Britain kept a cage bird. Linnets were the most popular of all because they were very numerous and huge numbers were taken from the wild to satisfy the whims of the time. 

Cock Linnet

 

Cock Linnet - August 2017

From “Every Woman's Encyclopaedia” circa 1910 -1912. 

 Every Woman's Encyclopaedia 1910-192

“There are five other members of the family of the Fringillinae which well deserve notice, as they are very suitable for pets. They are the linnet, siskin, redpoll, twite, and crossbill. 

The linnet claims the first place in popularity, and is one of the best of our British songsters. Its notes are very sweet and soft, although on this point individual birds vary, some being far better songsters than others. Old birds have a much fuller and better song than young birds, and are thus sought after by those who know of this characteristic. 

The cock linnet varies considerably at different periods of his life in the colours of his plumage, a fact which has led to the belief that there are several varieties of linnets, whilst, in reality, this variation in the colour of the plumage depends on the age of the bird. 

For instance, birds of a year old are called grey linnets, the feathers on the head and breast being edged with grey. Adult birds in the spring assume what is termed the breeding plumage, when the feathers on the head and breast become bright red, and the whole plumage brighter and more intense in colour. These birds are known as rose linnets. This red colouring quite disappears from birds in captivity. 

During the autumn and winter months the plumage of the adult birds becomes a rich brown, and they are then known as brown linnets. 

The plumage of the female bird does not vary, and is very similar to that of a young male bird. It is of a sombre colour, with less white on the wings and tail, and never possesses any crimson plumage on head and breast. 

The linnet is naturally a shy bird, but in confinement becomes quite tame and makes a very pleasing and interesting pet. In their wild state linnets become gregarious in winter, and may often be seen in the open country feeding on the seeds of wild mustard, sharlock, and other plants.” 

Stand by soon for more Linnet tales, old and new from Another Bird Blog.

Linking this post to  Stewart's World Bird Wednesday.