Finding Late Season Bird's Nest

 

                                                        Contents of Bluebird Nesting Box

With the nesting season over, autumn brings bird box maintenance.  One of our bluebird box poles was leaning and inspection revealed the 5" by 5" supporting pole broken at the base.  The break was into the ground so fortunately it did not interfere with the rearing of two clutches of bluebirds this summer.  The pole was removed, the base dug out and a new pole was prepared.  While transferring the box from one pole to the other, it was opened for cleaning.  Normally our boxes have about 2 inches of sawdust and wood shavings in the bottom.  A surprise awaited us on removing the face of the box.  There sitting on top of the wood shavings was a nest with eggs in it.  Well, whose eggs were these and what happened to the remains of the bluebird nest?  

                                                            Nest Found in Bluebird Box

The top photo shows the contents as removed from the bluebird box.  The nest is on top of the wood shavings with some of them incorporated into its structure.  The main nesting material is thick and made of coarse and fine grasses with a good addition of feathers.  The feathers look like chicken feathers probably from our neighbour's flock.  The nest contained 4 creamy coloured eggs with fine streaks and spots of reddish and dark brown.  My first comment on observing the contents was, 'Those are not bluebird eggs".  But whose were they?

                                                    Close-up of Eggs in Nest

The nest looked like the owner had just flown off for a morning forage.  However, we knew that was not so because the box is in close proximity to the house and is observed often.  The only activity there has been the flock of 4 to 8 Eastern Bluebirds which have been hanging around our yard this past week.  Although we have seen them peek into some of the boxes, they seemed interested only in perching on garden stakes and our various roofs in order to fly out to catch insects.  So what could these eggs be from?

Earlier in the summer we had a very active group of Tree Swallows using some of our nest boxes.  I think we had 4 successful broods raised.  The swallows have long since gone.  After they fledged they seemed to move out over the river to feed most of the time.  We have not seen a Tree Swallow in the yard for over a month now.  The only other activity we have seen has been a White-breasted Nuthatch pair which nested in another of our boxes last year.  This year we have not seen them around the boxes but they come regularly to the feeders.

                                                        Close-up of Egg Found in Nest

To solve the mystery we first measured the eggs with callipers:  18.4 mm by 13.2 mm (0.72 in by 0.52 in).  So we have rather small cream-coloured eggs with brownish spots and streaks.  That certainly rules out bluebirds which have pale bluish eggs.  So, what about Tree Swallows?  It turns out they have pure white eggs that are 19 mm X 14 mm (0.75 x 0.55 inches).  So we could rule out Tree Swallows.  They did not fit because we saw the bluebirds using the box after they had left the area.  

What about Black-capped Chickadees?  The literature says their eggs are white with reddish brown dots and are 0.55 X 0.45 inches.  Our mystery eggs were bigger than that and we had never seen the chickadees enter the boxes, although we could have missed it.  

So we are left with White-breasted Nuthatch as a possibility.  The literature says White-breasted Nuthatch eggs are 0.8 X 0.6 inches and white with brown and lilac speckles.  Our eggs fit into those dimensions but are just a bit smaller (0.72 X 0.52 inches).  And, the colour was right.  We concluded the mystery eggs came from a White-breasted Nuthatch.  

Let's look more closely at the nesting behaviour of this species.  The White-breasted Nuthatch is monogamous.  The pair remain together year round and stay together unless one partner dies or disappears.  Their territory is 0.1 to 0.15 Km squared (25-37 acres) in wooded areas and larger in semi-wooded habitat.  They usually nest in natural tree cavities or abandoned woodpecker holes. The nest is built 3 to 12 metres off the ground.  It is lined with fur, fine grass and shredded tree bark.  The eggs are incubated by the female for 13 to 14 days and the young fledge in 18 to 26 days.  Both adults feed the chicks both in the nest and for 2 weeks after fledging. After this period the young usually leave the adults' territory to find territory of their own.  

If the young are unsuccessful at finding their own territory, they become 'floaters'.  This is a term for an unpaired bird without a territory.  It is these floaters which are thought to make up irregular dispersal of bird species.  

White-breasted Nuthatches roost at night and in inclement weather in holes in trees.  We have observed them entering nesting boxes in cold weather.  They will also take shelter behind loose tree bark in order to avoid bad weather.  These birds usually roost alone but in cold weather they will join together presumably to preserve heat.  As many as 29 have been found roosting together!

So why did a White-breasted Nuthatch nest in this box after the bluebirds had raised 2 broods?  A White-breasted Nuthatch had nesting in a neighbouring box last year.  The collected nest contained no evidence of bluebird use but the nuthatch probably threw all of that out before building her nest.  It could be that the site of her previous nest had been predated or that it somehow was destroyed.  So why did she not remain on the eggs and finish her task?  She may have been taken by the Sharp-shinned Hawk that flew periodically through our yard.  Or, I suspect it was too late in the season to start a brood (which may also have been her second brood) and she had not become broody because of low hormones caused by the late season. 

All my theories are speculation but it is interesting to know that the White-breasted Nuthatch had somehow taken over the bluebird nest and nearly was able to raise her brood.  It will be interesting to see who uses the box next year.

Curlew Sandpiper - Ultra-Rare Vagrant from Europe

                        Curlew Sandpiper with Semi-palmated Sandpipers   [Jim Carroll Photo]

On 9 September 2021 Jim and Therese Carroll were birding at Red Head marsh near Saint John, NB.  Flocks of migrating shorebirds were present feeding on the marsh.  Shorebirds can be difficult to identify so they were looking carefully trying to find what species were there.  Going over flocks of peeps (small shorebirds) with their binoculars, Therese spotted something different, very different.  Using a telescope, they soon recognized what they were looking at was not anything any of us expected to see here in New Brunswick, a Curlew Sandpiper (Calidris ferruginea).  Fortunately Jim was able to capture some identifying photos which are shown here on this blog.  Many thanks to the Carrolls for finding and documenting this rare visitor!

Curlew Sandpipers have only been seen a few times in North America since accurate ornithological records have been kept.  There are a few records from the 1800s and in recent times we only have a small number.  According to A.C. Bent, Life Histories of North American Shore Birds, 1962, the Curlew Sandpiper was an occasional visitor to North America.  With the exception of one record from Point Barrow, AL all other occurrences have been from the eastern coast of North America (New Jersey 1829, Long Beach 1903, Cape May in 1868, Massachusetts in 1865); from Canada twice, from the eastern US about 10 times, from the West Indies twice and from Patagonia once.  The Canadian records were from Toronto (1868) and Nova Scotia.  

Recent sightings include two by our own Roger Burrows.  One in moulting plumage was seen and photographed in Newfoundland on July 15, 1985 at the Robin Hood Bay/ Cadet Road area of St. Johns by Doug Phelan and Roger Burrows.  Roger has also reported a juvenile from the Thoroughfare Road, Grand Manan on 9 September, 2009.  No photo was obtained from that sighting.

So where should this bird normally be?  In short, the species breeds on the eastern Siberian tundra and winters in central and south Africa, Asia and Australasia.  It passes through much of Europe and Asia on its migrations, following a different path north and south.  Its path north is more west than its path south.  It is seen in the British Isles in July to October; Denmark from August to October; on the Baltic shores, all Mediterranean countries, North Africa, Canary Islands, across Asia to the Indian Ocean, Malasia, China, Australia and New Zealand during migration. It is rare in Britain in spring but large flocks are seen around the eastern Mediterranean.  In spring migration it moves through some of Europe.  For example, it has been recorded from Gibraltar April 24, Egypt May 8, and also in April in Greece, Italy, Cyprus, and also at Lake Baikal and China.  That is a wide migration route! In fall it has been recorded from Ireland in August to September, Greece in September, Africa in November.  Casual records have been from Madagascar, New Zealand, Bering Island and North America.  In other words, it covers most of the Old World with some vagrants seen elsewhere.  This bird takes a very long migration route, sometimes up to 15,000 km.  That covers the distance from north-eastern Siberia to South Africa.  The breeding range of this bird is small (north-eastern Siberia).  Of all shorebird species, its breeding range is the smallest in comparison to its non-breeding range.  As rare as this species was/is in North America the records tell us that in 1844 there were a dozen specimens for sale at the Fulton market on Long Island.  

                                Curlew Sandpiper in Breeding Plumage   [Jim Carroll Photo]

Although the photos make one think we are discussing a rather large species, the Curlew Sandpiper is a peep, a small shorebird.  It is 22 cm long (8.5 inches).  Compare this to our very common Semi-palmated Sandpiper which is 16 cm (6.3 inches) long and the Dunlin to which it is closely related which is also 22 cm (8.5 inches) long.  The top photo shows the size difference compared to the Semi-palmated Sandpiper.  

The Curlew Sandpiper is described as more slender than the Dunlin but with longer wings, neck and legs.  The closest species we would have to distinguish it from are the Dunlin and the Stilt Sandpiper.  When the Curlew Sandpiper is in breeding plumage there is no problem.  The breeding plumage shows the beautiful rufous red colour on the breast, head, neck and sides.  The black bill is long and decurved.  The legs are black and medium-length.  The back is a mottled chestnut colour and the wings are grayish.  There is barring on the sides and under the tail.  In flight it shows a white rump which is a good feature to distinguish it from the Dunlin.  It also has a white wing stripe shown in flight which is used to distinguish it from the Stilt Sandpiper.  The female is similar to the male.  In non-breeding plumage the red fades and the birds become pale gray on the dorsal aspect and white below with a white supercilium.  The in-between plumage is a very interesting mottled gray and red with a mottled gray and brown back.  The juvenile shows a yellowish gray on the neck and upper breast on an otherwise gray and brownish plumage with white below.  I hope we get a chance some day to try to identify one of these plumages!

                                                   Curlew Sandpiper   [Jim Carroll Photo]

It is interesting to look at where this species got its name.  The 'Calidris' is from ancient Greek.  Kalidris was a term used by Aristotle which was used to mean a gray-coloured bird which stayed near the water.  Ferruginis is from Latin meaning iron rust and refers to the beautiful colour of the breeding plumage.  

                                                 Curlew Sandpiper   [Jim Carroll Photo]

Studying the courtship and breeding of this species has been difficult.  They are difficult to see on the Siberian tundra and early records were from people stranded on the tundra or iced in or Arctic boating expeditions.  Recent work has provided more data.  These birds arrive on the breeding grounds in Eastern Siberia in June.  They have been observed in small groups chasing one another around.  The male performs an aerial display for the female.  Nests are built on the drier part of the tundra on a gentle slope.  These areas are dotted with reindeer moss and tufts of wiry grass which are taller than the birds so they can hide easily from predators.  They can also get a wide field of view from these locations.  Several nesting pairs build nests in the same general area.  The nest is a deep hollow in the soil lined with mosses, lichens and leaves.  One nest was reported to have 4 eggs present in a deep hollow with the narrow, pointed end of each egg pointing downwards.  The eggs are pale yellowish-white with a greenish tinge and spotted with small blackish-brown which become confluent near the large end.  Nesting occurs even when there are still patches of snow on the ground.  Some researchers report that the small egg size and the bold markings make the eggs easily identified. The eggs are up to 39.6 mm long.  They are incubated for 21 days by the female.  After nesting both young and adults gather in large flocks and they stay on the tundra until autumn.

                                                 Curlew Sandpiper   [Jim Carroll Photo]

Curlew Sandpipers feed on insects, snails, marine worms, crustaceans, small molluscs and some vegetable matter.  They forage by probing the mud rapidly while walking.  They will wade belly-deep in the water while probing.  This species is not very vocal but on the breeding grounds their alarm call is a rapid 'wick, wick, wick'.  Their flight call is somewhat like that of the Dunlin but purer in tone and sounds like, 'kril'l'l'lee'.

The population numbers of the Curlew Sandpiper are in trouble like most shorebird species of the world.  Counts have been done in South Africa where they are most numerous and the counts show a 40% decline from 1975 to 2009.  The effects of global warming on their breeding grounds, pollution and habitat loss are some reasons for this decline.  Population numbers also flucuate with the populations of lemmings in the north.  If lemming numbers are down, then Skuas and Snowy Owls will prey on nesting shorebirds including the Curlew Sandpiper.  The Curlew Sandpiper is protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds.

                                                 Curlew Sandpiper   [Jim Carroll Photo]

The Curlew Sandpiper occasionally hybridizes with the Sharp-tailed Sandpiper or the Pectoral Sandpiper.  The Curlew/Sharp-tailed cross is called the 'Cooper's Sandpiper'.  The Curlew/Pectoral cross is called the 'Cox's Sandpiper'.  

Whimbrels on Miscou

                                                                            Whimbrel

Whimbrels are large shorebirds that stop along our coastal areas during fall migration.  They stop here to feed and  build up their energy stores before continuing on their very long migration leg to South America.  Our feeding areas here in New Brunswick are vital to their survival.  

Whimbrels are large sandpipers 44 cm long with a wingspan of 81 cm (17.5 in, 32 in).  They are uniformly speckled, brownish on the back, head, sides and tail and grayish on the underneath.  Their most notable identifying feature is their long decurved bill.  They also have very pointed wings.  

In the fall Whimbrels move in small scattered flocks.  They may spend several days in one feeding area usually on coastal heaths, shorelines, marshes and mudflats.  In the west they also spend time on the prairies.  Their main foods are marine invertebrates, marine worms, molluscs, fish, insects and berries.  On Miscou they are found mainly on the heath but also on shorelines, grassy areas and fields.  

                                                        Whimbrel on Heath of Miscou

Recently, in the first week of August we visited Miscou in search of the whimbrels.  We don't always find them because they are difficult to see but this year we saw 3.  If they are on shorelines and mudflats they are usually fairly easy to spot.  On the heath, however, they are very difficult to see.  The heath is mainly low woody plants forming a thick shrubby layer that is almost impenetrable except by machine.  The shrubby plants are about 0.5 to 1 metre tall.  Among these plants are crowberries (Empetrum nigrum) and various kinds of blueberries (Vaccinium) on which the birds feed to build up their fat stores for energy to migrate south.  They also feed on snails, worms and insects found among the plants.  Because the birds are wandering both deep among the plants and sometimes on top, they are difficult to see.  The vast acreage covered by this vegetation on Miscou makes it difficult to see the birds.  Given that one can see for many kilometres over the heath, you can imagine how difficult it is to spot the birds.  Getting a good photograph is very difficult.  See below for a typical exposure.

                                        Whimbrel Shown Among the Heath Plants

Whimbrels are one of our notable shorebird species.  We have a moral duty to protect their habitat so that they can successfully make their migrations.  After all they are making their way from the tundra of coastal Nunavut, Northwest Territories, Alaska and James Bay to South America where they will spend the winter.  We are graced with their presence and it is a delight to get a peek at their presence as they stock up on our available food.   They have been coming here for 1000s of years.

To see more on Whimbrels, search this blog for 'Whimbrel'.