Feathery Competition on Golf Courses - USGA Green Section Record

Pole-mounted nest box with predator guard.found to use these next boxes besidesnuthatches and bluebirds. Theyincluded Carolina chickadees, housesparrows, tree swallows, tufted titmice,house wrens, and even southern flyingsquirrels. However, it was the rarity ofnuthatches that had these scientistsasking, “Why?”Researchers acknowledge thatpopulation declines are likely due,in part, to extensive logging, whichlimits cavity-nest sites for this species,although they suspected other factors.“Habitat degradation continues to bethe major cause of population declinesfor many birds. But we often lack anuanced understanding of how particularhabitat deficits impact the birds inquestion,” says Dr. Stanback, projectleader.Dr. Stanback and his colleagueswere determined to identify factorsthat were contributing to the lack ofobserved nuthatches in the samplednest boxes, and to determine what, ifanything, could be done to reverse thistrend. The first question was, “Doescompetition with bluebirds over nestboxes prevent breeding bynuthatches?”To answer this question, they hadto exclude bluebirds from the nestboxes. The standard nest boxes wereequipped with a 38-mm (1.5-inch)entry hole, which accommodatesbluebirds and all other smaller cavitynesters.Prior to the 2005 season, onapproximately a quarter of the boxeson four of the golf courses, theyreplaced front plates with ones with28-mm (1.1-inch) holes to exclude thelarger bluebirds. Prior to the 2008season, hole size was reduced onanother one-third of the nest boxes ontwo additional courses. The resultsclearly showed that when competitionfrom bluebirds for nest boxes waseliminated in this way, significantlymore nuthatches used those boxes tosuccessfully fledge their young.“For several years my students and Iobserved occasional nesting attemptsby brown-headed nuthatches on golfcourses where we were studyingbluebirds. However, most ended withbluebirds taking over the boxes. Theseusurpations prompted me to hypothesizethat bluebirds were monopolizinggolf course nest boxes, and that onlyby excluding them could we see whatnuthatches were capable of,” explainsDr. Stanback. “Seeing so manysuccessful nuthatch nests was veryheartwarming. Nuthatches live inlarge family groups and are verycharismatic — you can’t help but rootfor the little guys.”Dr. Stanback and his colleaguesnote that nuthatches have beenhistorically associated with maturepine forests, so the second questionthey wanted to investigate was, “Towhat extent is nest box occupancy bynuthatches dependent on the proximityGreen Section Record Vol. 50 (3)February 3, 2012 Page 2

of pine forests?” Stanback and histeam carefully categorized the nestbox proximity to the three nearest pinetrees and monitored the use of boththese large- and small-hole nest boxeson four golf courses. They found thatneither bluebirds nor nuthatchesshowed preference regarding pinedensity, although nuthatches usedbluebird-proof nest boxes with smallerholes far more than expected.“The conventional wisdom is thatthese nuthatches require mature pinestands,” says Dr. Stanback. “While Irecognize that brown-headed nuthatchesneed some pines, I wassurprised that the minimum was so . . .minimal. We had successful nuthatchnests in open fields with no pines insight. The key really does seem to beprevention by bluebirds.”The third question Dr. Stanbackand his colleagues asked was, “Canbluebirds actively displace nuthatchesfrom nest boxes?” To answer this, theyincreased the size of the entry holes(making them bluebird-accessible) onnest boxes that were previouslybluebird-proof (having smaller entryholes) and contained nuthatch nests in2007. The results were overwhelming.Nearly all of the 32 boxes used bynuthatches in 2007 were used bybluebirds in 2008 after the size of theentry holes was increased. In mostcases, bluebirds evicted nuthatchesthat were beginning to build nests.The results clearly indicated thatnest box occupancy favored bluebirdswhen the entry hole was large (1.5inches), but when bluebirds wereexcluded using smaller entry holes (1.1inches), nuthatches readily occupiednest boxes. The researchers asked thenext logical question, “Could pairingstandard (with larger holes) boxesallow bluebirds and nuthatches tocoexist?” In 2009, researchers pairedup most of the nest boxes at the localsix golf courses. Paired nest boxeswere typically 10 meters apart and hadone nest box with a small hole and onebox with a larger hole, both nest boxeswith large holes, or both with smallholes.Results indicated that bluebirdswould not allow nuthatches to nest inadjacent larger-holed nest boxes, evenwhen bluebirds nested in only one oftwo larger-holed nest boxes. However,when the pair of nest boxes includedone small and one large entry hole,nuthatches were able to nest in thesmall-hole nest box in 74 out of the 139big/small box pairs. Thus, while pairingidentical larger-hole boxes may be aneffective strategy for some species,nuthatches appear not to benefit inany way from this practice.“Nest boxes can be incrediblyeffective conservation tools,” saysDr. Stanback. “For example, bluebirdlovers have increased bluebird numbersdramatically in recent decadessimply by making nest boxes availableto them. However, bluebirds are almosttoo good at taking advantage of nestboxes. A golf course superintendentwho installs 18 nest boxes may feelthat he is doing something great for allbirds. The fact is, 16 of those boxes willcontain bluebirds, and if another 18boxes are installed, it will probably justresult in 16 more bluebird families.Brown-headed nuthatches need someboxes specifically set aside for them.Changing the size of the entry hole creates a bluebird-accessible nest box (left)versus a bluebird-proof nest box (right).Green Section Record Vol. 50 (3)February 3, 2012 Page 3

0.60.8■ EABL OnlyProportion of AvailableBoxes Occupied0.50.40.30.20.1Proportion of AvailableBoxes Occupied0.70.60.50.40.30.20.1■ EABL/BHNU0Big HolesSmall Holes0Big BigBig SmallProportion of bluebird-accessible (big holes) andbluebird-proof (small holes) nest boxes containingsuccessful nuthatch nests. Thirty percent of the boxeswere made bluebird-proof by reducing the hole sizeStanback, 2011). Results show that nuthatches weresuccessful in nesting only after the hole size of the nestbox was reduced, restricting access by bluebirds, butstill allowing access by nuthatches.When researchers used pairs of nest boxes each with big holes(big-big), bluebirds (EABL) monopolized nesting and inhibitednesting by nuthatches, even if bluebirds did not nest in one of thebig-holed nest boxes of the pair. When pairs of nest boxes hadboth a big-holed nest box and a small-holed nest box (big-small),nuthatches (BHNU) were able to nest successfully in the smallholednest box, even when bluebirds nested in the adjacentbig-holed nest box of the pair.“Let me be clear. I’m not advocatingthat anyone ban bluebirds. However, Ialso believe that most bluebird loverswould be willing to set aside a portionof their boxes for the benefit of acharismatic, cooperatively breeding,and threatened southeastern endemicbird, too.”After completing this work, Dr.Stanback and his colleagues areconvinced that southeastern golfcourses can make an impact in helpingto bolster the populations of brownheadednuthatches, especially coursesthat already provide nest boxes forbluebirds.“I think southeastern golf coursesoffer real potential to help nuthatches,just as they have boosted bluebirdpopulations. Most contain enoughpines to harbor at least some nuthatches— and the spacing of treesand open understory that characterizemany southeastern golf coursesmimics aspects of their ancestralhabitat,” explains Dr. Stanback. “Bluebird-proofnest boxes really work. Atsome of our courses, we have gonefrom zero to 20 successful nuthatchnests in just a few years. Moreover,participating golf courses can act ascritical ‘source populations’ that act tomaintain or restore nuthatches to surroundingareas. Because the Southeastwill continue to suburbanize, golfcourses can help brown-headed nuthatchessurvive, and perhaps eventhrive in this transition.”This work demonstrates yet anotherinstance where golf courses can assistMother Nature. Dr. Stanback and hiscolleagues make the following recommendationsto superintendents of themore than 4,000 golf courses in NorthCarolina, South Carolina, Georgia,Florida, Alabama, Mississippi,Louisiana, and east Texas:● Even golf courses without extensivepine stands can benefit brownheadednuthatches by providingnest boxes.● Nest boxes should be pole-mountedwith predator guards and should becleaned out each autumn.● There is no need to pair boxes toincrease occupancy by nuthatches.● Every other box should have a oneinchentrance hole to accommodatebrown-headed nuthatches (andCarolina chickadees), but excludebluebirds and house sparrows.● Consider retrofitting a number ofexisting bluebird-accessible boxesusing a metal disc with a one-inchhole.LITERATURE CITEDButcher G. S., D. K. Niven, A. O.Panjabi, d. N. Pashley, and K. V.Rosenberg. 2007. The 2007 Watch Listfor United States Birds. AmericanBirds 61:18-25Jackson, A. K., and D. A. Cristol.2011. Tracking survival of bluebirds ongolf courses. USGA Turfgrass andEnvironmental Research Online10(6):1-7. (TGIF Record Number177045)Stanback, M., E. Cline, W. Anderson,L. Bergner, P. McGovern, A.Mercadante, D. Millican, and J. Olbert.2011. Bluebird-proof nest boxesincrease brown-headed nuthatchbreeding on southeastern golf courses.USGA Turfgrass and EnvironmentalResearch Online 10(18):1-12. (TGIFRecord Number 189040)JEFF NUS, Ph.D., manager, GreenSection Research.Green Section Record Vol. 50 (3)February 3, 2012 Page 4