Fly­ing under the radar

At the end of the open­ing morn­ing of Duck Sea­son in South Aus­tralia, hun­ters on the Cortina lakes were asked for their as­sess­ment of Blue-winged shov­eler num­bers as part of an in­for­mal re­search project. “Enough to have at least a cou­ple in the bag,” one h

Field and Game - - BLUE-WINGED SHOVELER -

This isn’t sci­ence by any stretch of the imag­i­na­tion, but in the ab­sence of any at­tempt to pro­duce a more rig­or­ous as­sess­ment, it is at least some­thing. Al­most uni­ver­sally, the as­sess­ment of hun­ters, who have a keen eye and are fre­quently shar­ing the same habi­tat as the shov­eler, is con­trary to the aerial sur­veys. This cen­tury, the Eastern Aus­tralia Water­bird Sur­vey has recorded very lim­ited num­bers of shov­eler, yet hun­ters see them all the time. The sur­vey has recorded sig­nif­i­cant num­bers in the past, in­clud­ing more than 20 000 fol­low­ing the floods of the early 1980s and sim­i­lar spikes fol­low­ing ev­ery drought break­ing flood event since, but in be­tween the ob­served num­bers flat line.

Un­der­stand­ably, hun­ters ques­tion whether the ob­served num­bers of shov­el­ers in the an­nual aerial sur­veys in­di­cate low abun­dance, or just the dif­fi­culty in re­li­ably count­ing them from an air­craft.

The only way to an­swer that ques­tion is to ap­ply sci­ence, some­thing Field & Game Aus­tralia is pur­su­ing.

Our sci­en­tific knowl­edge of Aus­tralian ducks in gen­eral is poor and very lit­tle has been done to build on the land­mark work of Harold James (Harry) Frith in the mid­dle of last cen­tury.

Frith re­ceived a copy of the first edi­tion of Cay­ley’s What Bird is That? for his tenth birth­day. He later ded­i­cated his ma­jor work, Wa­ter­fowl in Aus­tralia, “to my fa­ther who taught me about birds”.

Frith’s pioneer­ing stud­ies on the breed­ing, feed­ing and move­ment of Aus­tralian ducks are con­sid­ered his ma­jor con­tri­bu­tion to ecol­ogy. In a se­ries of re­search pa­pers ti­tled The

Ecol­ogy of Wild Ducks in NSW, Frith de­tailed the re­sponse of the main wild duck species (Pa­cific black duck, Grey teal, and Wood

duck) to rain­fall events.

A large-scale band­ing pro­gram re­vealed the ap­par­ent ran­dom scat­ter­ing of wild ducks from wet­lands where wa­ter and/or food was be­com­ing scarce was not the full story.

In 1957, Grey teal banded at Gum Creek in NSW were trapped on Humpty Doo sta­tion in the North­ern Ter­ri­tory, show­ing the vast dis­tance they would travel to find suit­able feed­ing grounds.

Frith recorded that the indige­nous pop­u­la­tion was un­able to recog­nise it, thus sup­port­ing the au­thor’s im­pres­sion the Grey teal very rarely vis­its that re­gion.

In 1953, Frith be­gan band­ing ducks and over the decade the shifts from flood to drought across the Mur­ray-dar­ling area al­lowed him to ob­serve the marked ef­fect on duck be­hav­iour and pop­u­la­tions.

In 1955 dur­ing a mi­nor flood down the Lach­lan River, Frith hunted sev­eral ducks and found their testes were sex­u­ally ma­ture. He then drove 160 km to get ahead of the flood­wa­ters and hunted sev­eral more ducks. Their testes were sex­u­ally in­ac­tive.

It was for Frith dra­matic con­fir­ma­tion of what he had be­gun to sus­pect: that breed­ing was linked to wa­ter lev­els.

Con­sec­u­tive flood years in 1956 and 1957 pro­vided the nat­u­ral lab­o­ra­tory to ev­i­dence how ducks adapted to their un­pre­dictable en­vi­ron­ment to en­sure the con­tin­u­a­tion of their species.

Frith had a knack of mak­ing his own luck.

In 1957, while in­ves­ti­gat­ing the im­pact of Mag­pie geese on crops around Dar­win, Frith wit­nessed Grey teal be­gan ar­riv­ing in their thou­sands. He phoned an ur­gent re­quest for traps and banded 5000 birds.

Over the years, the bands re­cov­ered from those birds re­vealed an ex­tra­or­di­nary pat­tern of ex­plo­sive dis­per­sal in times of drought.

Later work showed that in times of drought Grey teal might not breed for sev­eral years, yet within only 10 days of an in­crease in wa­ter level they could be­come sex­u­ally ac­tive and lay eggs.

Decades be­fore the controversial Mur­ray-dar­ling Basin Plan was struck, Harry Frith fore­shad­owed the need for ac­tion.

“When hy­dro­elec­tric and ir­ri­ga­tion schemes fi­nally con­trol all floods, the Grey teal and many other wa­ter­fowl will have few places left to breed,” he said. “To pre­vent this, the re­plen­ish­ment of bil­l­abongs along in­land rivers must be en­sured and the coastal swamp refuges pro­tected. Most im­por­tantly, the states and the Fed­eral Gov­ern­ment must agree on a com­mon re­source pol­icy and in­volve bi­ol­o­gists in the plan­ning of wa­ter con­ser­va­tion.”

Frith’s sem­i­nal works greatly en­hanced our un­der­stand­ing of wild ducks, but Bluewinged shov­eler were not banded as part of his work dur­ing the 1950s.

The na­tional bird band­ing data­base records only 23 banded shov­el­ers, the earliest in Fe­bru­ary, 1956 and the last in March, 2014.

Only three bands have been re­cov­ered, in­clud­ing a bird banded in De­cem­ber, 1959 at Joanna, SA that was found dead 10.5 years later near Wol­langambe, NSW.

Har­vest data is avail­able but in iso­la­tion, it adds lit­tle to our knowl­edge of dis­tri­bu­tion and mi­gra­tion move­ments.

Frith’s shov­eler ob­ser­va­tions in the 1950s were lim­ited to nest­ing pref­er­ences.

Shov­eler have a very wide range: in eastern Aus­tralia it can be found from as far south as Tasmania to Cairns in the north, but it is also found in New Zealand where it is known as the Aus­tralasian shov­eler.

Across the ditch, sig­nif­i­cantly more re­search has been done into move­ment and mor­bid­ity of shov­eler, but it does not sub­sti­tute for knowl­edge gained in the spe­cific Aus­tralian con­text.

There is an op­por­tu­nity to broaden our un­der­stand­ing of our least un­der­stood Wood duck species.

The In­ter­na­tional Co­op­er­a­tion for An­i­mal Re­search Us­ing Space (ICARUS) Ini­tia­tive is open­ing new av­enues to ob­serve mi­gra­tory move­ments of small an­i­mals and birds through a satel­lite sys­tem.

De­scribed as the “In­ter­net of an­i­mals” the project al­lows re­searchers to fit a tiny sen­sor-laden tag to small crea­tures like ducks. The tags have a GPS re­ceiver, 3D ac­celerom­e­ter, and tem­per­a­ture, hu­mid­ity, pressure, al­ti­tude, and heart rate sen­sors. The tags are also equipped with so­lar pan­els and recharge­able bat­ter­ies.

The tags store data and send in batches to a com­puter aboard the In­ter­na­tional Space Sta­tion, which pro­cesses the in­for­ma­tion and beams it down to earth. The small­est tag weighs 2.5 g. It is a long way from the im­age of Harry Frith climb­ing trees in swamps to ob­serve breed­ing be­hav­iour. Frith’s work re­mains im­por­tant, but it is time to build on our knowl­edge of our unique duck species, start­ing with the Blue-winged shov­eler.

Aus­tralasian Shov­eler — Anas rhyn­cho­tis. Photo; Judy Gallagher

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