TURF WAR TWIST

Why mountain bluebirds have disappeared from western Montana’s valleys— and might never return.

By Renée A. Duckworth and Alexander V. Badyaev

K A N Z O L

N I

B IN FOR THE DURATION Secure in man-made nesting structures, O R

Y

B western bluebirds no longer face the historical loss of nesting

D R I

B trees toppled by age and wind. ﬔe authors maintain that the E U L B

boxes are good for this species in western Montana valleys but N R E

T don’t benefit, in the long run, mountain bluebirds, which require S E

W a cycle of fire and new cavities to colonize low-elevation areas.

30 MARCH ?APRIL 2014 FWP.MT.GOV/MTOUTDOORS MONTANA OUTDOORS 31 1. Periodic forest fires 2. ...the cavities of which bution. We learned that the historical cycle kill low-elevation are excavated by ne morning in March $''', just like trees... in which the two bluebird species displace woodpeckers and then colonized by widely every year for the previous &# years or one another every 20 or so generations has dispersing mountain been disrupted. And the cause, ironically, bluebirds... so, the late Joe Waldbillig—a cattle has been the creation and maintenance of new nesting habitats. began to re-colonize their historical Mon - rancher and self-taught naturalist—was tana range. Just as in times past, the two driving his pickup down the snowy road FIRE-INDUCED CYCLE bluebird species were back. Historically in Montana, western bluebirds HISTORICAL bisecting his western Montana ranch. and mountain bluebirds more or less co - WITNESSING HISTORICAL PATTERNS existed in the forested river valleys west of 20> TO 30>YEAR What was so exciting for us as scientists was ORanging in elevation from %,### to &,### feet, the ranch was the Continental Divide (another species, the the opportunity provided by the bluebird eastern bluebird, lives east of Great Falls). CYCLE boxes to observe the patterns of historical col - a haven for mountain bluebirds, and every day through early The relationship worked like this: Blue - onization and competition between the two birds nest in tree cavities but, unlike wood - species. It was as though the slate had been sprin g Waldbillig drove around the valley looking for signs of peckers, cannot make their own. After a DISRUPTION wiped clean and the birds had to reform their wildfire, woodpeckers colonize burned Bluebird nesting relationships before our very eyes. the birds’ return as indication that the worst of winter was over. boxes create areas, and, in less than a year, numerous permanent homes We documented how newly arriving But that morning, much to his surprise, he such stories of rapid replacement of one cavities in dead and decaying trees provide for western bluebirds. western bluebirds started to rapidly replace came across a bluebird species he had never bluebird species by the other would repeat prime nesting real estate for bluebirds. With no new valley mountain bluebirds in the valleys of west - fires to “re-set” the before seen on his ranch: an industrious itself over and over on our 15 western Mon - The first to arrive are mountain blue - historical cycle, 3. ...which are driven ern Montana. In only 15 to 20 years, we male western bluebird, inspecting nest tana study areas, which included the Wald - birds, more wide-ranging than westerns and mountain bluebirds into the mountains watched many of our research sites go from by the aggressive boxes along the fence. billig ranch, where we monitored these able to find new habitat quickly. Then the are now restricted no bluebirds, to 100 percent mountain to higher elevations. type of western It was a preview of momentous changes. remarkable relationships . Since 1995 we have more aggressive, but less mobile, western bluebirds... bluebirds, to 100 percent western blue - 4. ...which are eventually joined by In just five years, Waldbillig would witness on been investigating competitive interactions bluebirds arrive and outcompete the moun - the peaceful, home-loving type of birds. When we conducted a census of nest - his ranch the near complete takeover of between mountain bluebirds and western tain bluebirds for nest sites. The mountain western bluebirds, until.... ing bluebirds in a popular recreation area mountain bluebirds by the newly arriving bluebirds to understand the mechanisms bluebirds retreat to the mountains, where near Missoula in the early 1990s, all but one western bluebirds. Over the next decade, underlying these dramatic changes in distri - they can survive but western bluebirds can - breeding pair were mountain bluebirds. By not, waiting for the next cycle of valley wild - five or more boxes placed roughly 100 to the early 2000s, the mountain bluebirds fire to re-set the process and start over. This 300 yards apart, often along highways and were gone, completely replaced with a went on for thousands of years. country roads. much higher density of western bluebirds. But starting around the late 1930s, the As hoped, bluebird populations began to Five years ago, the western bluebird was a western Montana river valley landscape recover. First mountain bluebirds reclaimed rare visitor in the Blackfoot-Clearwater changed more drastically than at any time their historical lower-elevation areas. Then Wildlife Management Area near Ovando. since the last ice age. Many bottomland western bluebirds, which had retreated to Today the bird is common throughout the M O

C forests were logged and replaced with lush bottomland refuges farther west and south, entire Blackfoot Valley. . K C O T

S fields of wheat, alfalfa, and other crops. R E T T

U Forest fires were suppressed. Populations of H S

: E C

R western bluebirds, a species generally U O S

S confined to lower-elevation valleys, were With trees no longer C I H P A

R devastated by the loss of nesting cavities. By G

E L

C dominating the valley

Y the mid-1940s they had nearly disappeared C

L A C I

R from Montana. Although mountain blue - O

T floors as in the past and S I H birds also lost nesting sites, they had evolved ; V E A Y

D to also use habitats at higher elevations, A no periodic “re-setting” B

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R where forests remained largely intact. E D N A X In the early 1970s, conservation-minded of the cycle by natural E L A

: S

O Montanans began an ambitious effort to T O H

P wildfires, the dynamics

X restore low-elevation bluebirds by nailing O B

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I wooden nest boxes to fence posts. Over the B E of coexistence between U L B

next several decades, volunteers with the PERIODIC VALLEY VISITOR Historically mountain bluebirds lived in low-elevation areas for D N A

E nonprofit group Mountain Bluebird Trails G

several years until driven into high country by aggressive western bluebirds. ﬔe situation would A these two species have P

E T remain static until old snags toppled, driving out the western bluebirds, and forest fires I placed more than 8,000 nesting structures S O P P

created new dead trees that attracted the more widely dispersing mountain bluebirds. O along what are known as bluebird “trails”— fundamentally changed.

32 MARCH ?APRIL 2014 FWP.MT.GOV/MTOUTDOORS MONTANA OUTDOORS 33 For the time being, it seems that western bluebirds will dominate low elevations and mountain bluebirds will be restricted to the high country.

We set out to find out why western blue - ulation, a young male western bluebird has must stay on the nest to keep eggs or Is there a way to “re-set” dynamics of coexistence between these tain bluebirds beforehand, as occurs in low- birds are so successful at displacing moun - two choices—either assist his parents in rais - nestlings warm during the cold, she can’t two species have fundamentally changed. lying areas. Unfortunately for the species, the tain bluebirds and found an important ing their young and then inherit a part of their forage on her own. Nonaggressive males the historical cycle so eggs or nestlings of the pushy western male behavioral difference. Western bluebirds are territory (and thereafter nest near his birth - bring her nearly all her food during these BOXED OUT and his mate quickly perish in the harsh more aggressive and also breed at higher place), or disperse and compete for a territory times, and consequently the family’s broods that mountain bluebirds Without question, nesting boxes have been a mountainous conditions. The western blue - densities. Once they arrive in an area and in a new area. We found that the strategy a tend to survive the nesting season storms. boon to bluebirds. Without them, we’d see birds’ Achilles’ heel—the inability of aggres - start to breed, they crowd out mountain male pursues depends closely on his aggres - Aggressive males, on the other hand, might make their way very few western bluebirds in Montana. But sive males to feed their incubating and bluebirds. This, we discovered, is because siveness. Belligerent males are more likely to hardly ever feed their mates, so their nests back to the valleys of they have had unintended consequences. brooding females during late-spring snow - the westerns have two distinct behavioral leave their home ground and disperse to new rarely survive late-spring cold snaps. This The constant nature of the man-made struc - storms—creates a safe haven for mountain strategies that allow them to successfully areas to breed, while peace-loving males re - greatly limits the western bluebird’s ability western Montana? tures, replaced by bluebird fans as soon as bluebirds at higher elevations. colonize habitats newly created by fire and, main in their natal population and eventually to establish in a new area until enough mel - they break down, has disrupted the natural Is there a way to “re-set” the historical at the same time, maintain previously estab - acquire a territory near relatives. low males establish themselves in the pop - cycle of repeated colonization. Many lower- cycle so that mountain bluebirds might lished populations. Dispersing to new areas with a low den - ulation to ensure a secure base from which cycle would play out all over again. Moun - elevation valleys in western Montana are now make their way back to the valleys of west - The species is what’s known to biologists sity of other western bluebirds means that the bold males can continue dispersing. tain bluebirds would find new fire-created home to stable populations of western blue - ern Montana? Probably not—at least not in as a “facultative cooperative breeder”— aggressive males acquire larger territories Historically, the combination of aggres - nesting sites first, and then the aggressive birds that have permanently replaced moun - a way that mimics natural forest succession. O T N E meaning that some adult offspring postpone than they would have obtained in a crowded sive explorers and nurturing settlers enabled M type of westerns would start to displace tain bluebirds. For the time being, it seems But there is a way for these delightful bird R A S

. M breeding for a year or two to help their par - natal area. And nonaggressive males, despite the western bluebird to colonize new areas them. Over time, once mountain bluebirds that western bluebirds will dominate low el - species to coexist. Some nest boxes could be Y E L S ents and relatives raise nestlings. In any pop - being poor competitors, can still obtain a ter - and displace the more widely dispersing E were completely gone, the peaceful type of evations and most mountain bluebirds will be installed 300 yards or farther apart. Mountain W

; V E A

ritory from their parents and start a family of mountain bluebirds that had arrived in Y westerns would join the bolder birds—until restricted to high country. bluebirds don’t stick around when western D A B

. V their own if they stay near their birthplace. newly burned areas before them. But even - the next fire re-set the cycle once again. Why can’t western bluebirds take over the bluebirds are too close. If mountain bluebirds R E D N

What’s more, the gentle males are superb tually, old trees with cavities would topple A These fire-induced dynamics began to higher elevations, too? Like the peaceful type can stay far enough away from western blue - X E L A

;

providers, something essential during late- while new live trees without cavities would V change as farms and ranches reshaped of western bluebird male, the male mountain bird boxes, they won’t leave. An ideal bluebird E A Y D

A Montana and natural nesting cavities, cre -

spring snowstorms that are common in grow. Lacking nesting habitat, bluebirds of B bluebird is a great provider, allowing his and trail in western Montana, in areas where both

. V

R E ated by wildfire, were replaced with thou -

Montana and the chief cause of bluebird egg both species would be forced to search for D his mate’s nest to survive late-spring snow - species still occur, would have boxes placed N A X E

and nestling mortality. Because the female new patches of habitat elsewhere, and the L sands of more or less permanent nest storms, more common at 6,000-foot eleva - at varying distances. Because bottomland A

: T F E

L boxes. Unlike natural cavities, nest boxes tions and higher. The peace-loving western forests and accompanying wildfires are a M O T T are a “constant habitat.” With trees no Renée Duckworth (left), an ornithologist and ecologist at the University of Arizona, has O bluebird type could likely survive in the thing of the past, this might be the only way B

M O

been studying Montana bluebird coexistence dynamics for two decades. Alex Badyaev, R longer dominating the valley floors as in mountains, thanks to the male’s food-deliv - for people to enjoy seeing both species of F

E S I

an evolutionary biologist at the University of Arizona, divides his time between long-term W centuries past and no periodic “re-setting” ery service to his nesting mate. But it would these cheery, charismatic birds in the same K C O L

field research projects in northern Montana and southern Arizona. C of the cycle by natural wildfires, the need the aggressive type to drive out moun - general area.

34 MARCH ?APRIL 2014 FWP.MT.GOV/MTOUTDOORS MONTANA OUTDOORS 35