NorthwestScience Notes

Thepurpose oJ Notesis to pubLishpupers typicalll les.;thanJive pages Long No speciJic.form(tot' ctnlent is retluireclJbr articlesltublished as Notes,but ctll will be peer'teviewed dnd must he scientiJicall cretlible. Authorsnay ctntacl the Editor about the suitabili6 of xt ruscriptsfor this section.

W H. Rickard, State tlnverstyTri Cltles,2Tl0UniverstyDrve Rchland Washngton 99352 ano BrettTiller,l Pac f c NorthwestNat ona Laboratory,PO. Box999, R ch and,Washington 99352

Observationson the NestingDistribution of GreatBlue Herons on the HanfordReach of the ColumbiaRiver

lntroduction Methods The Hanford Reachis an 80-km segmentof the Information concerningthe distributionof heron ColumbiaRiver extending downstream from Priest nests along the Reach was obtaincd fuom pub- RapidsDam to near Richlandin southcentral li.hcdliterature rnd per.onillohser\ ation. .in. c Washington(Figure l). This segmentdiffers fiom the 1970s.In thc years1994 to 2001 counts()1' the rest 0f the river upstreamfrom tidewaterbe- activenests were madeby visitingcolonies all causeit is notimpounded by a dam(Geist 1995). along the reach in July and August when the ac- Heremost ofthe riverflows throughfederalprop tive nestswere identified by the prescnceof pre- eny () but the easternshore down- flight nestlings.Becausc road access to the shore- streamfrom SavageIsland is private (Figure 1). line is limited the colonieswere accessed by boat. Land use on the Hanford Site dilltrs from sur- rounding landscapesbecause towns and irrigated Results fields have been abandonedsince 194'1.Public (Ardeaherorlia.s), accessto the river shorehas been restrictedbe- In 1950twelve greatbl:uehercr. (Morr.! causeof the presenceof nine plutonium produc- nestswere placedin two mulberry trees tion reactorsat six separatelocations along the nlla), on Locke Island (Figure l). At that time westernrivershore (Figure l). Since 194'1,thc thesewere the only greatblue heron nestson the Hanford Site has servedas a refugium tbr native Reach(Hanson 1968). plantsand wildlife in a larger surroundingregion Most of the heron nestson the Reach since devotedto cultivation agriculture and urbaniza- 1950have been placed in lreesplanted a1 now don (Gray and Rickard 1989). The purposeof abandonedf'armhouses near the dver shorein the this note is to summarizeobseruations concem- early1900s (Figure 1). These trces, mostly black ing the distribution of great blue herons (AnCea locust(Robinia pse udo-atacla), and Siberianelnr herodias) dong the Hantbrd Reach.This is im- (lJlmuspunila),havc survivedin this dry climate portantbecause it providessome insight asto the t l6 Lm rnnualllt in theab.ence ,'l irrigrtionu a- ability of great blue heronsto adapt to an envi- ter becausethey haveroot accassto a watertable ronment changingin responseto the activitiesof <10 m below the ground surl'ace(fuckard and people. Price 1989).These trees are senescent and vul- nerablc to wildfire, windfall and insect infesta- 'Au|hor to \lhom cofiesponderceshould be addrcssed tion. Their future is limited. Many recently E mail: [email protected] selfestablishednative and alien trees now grow

No hwestScience, Vol. 77, No.4,2003 357

O lirol b) rhe\onhtr.n S.ieniiii.Arni.ri!on Allri-hr' re.entd A HeronColonies f-r'l HanfordReactors 4 -_--- 0 4 8 12 Kilometers

Figurc 1. Map ofthe Hanlbrd Reachofthe Colunbia River. showing lhe distribution ofheron colonics.

358 NonhwestScience. Vol.77, No. 4, 2003 on riverine beachesthat historically were devoid summerof 1994.Heron nests at the islandcolony of trees (Snodgrass1904). The spreadof these 1I were locatedin a tall, steel transmissionline selfestablishedtrees is apparentlyencouraged by louer(Tablel) In lq94rhere\\erel6acrirenests the diumally fluctuating fiver flow regulatedby in the towerand 12in 1995(Table 1). In 1996a upiver hydroelectric dams (Rickard and Poole rcd-tailed hawk (8,.,teo jqm(ric ensis')rrcsted. in lhe 1989). These newly establishedtrees may pro towerandthere were no activehercn nests in 1998, vide heron nest sites in the future but observa- 1999.and 2001.Colony 6 was useduntil 1998 tions show that only self-establishedtrees on is- when a pair of bald eagles (Haliueetus land shoreshave been selectedas nesting sites. leu<'ocephalus) began nesting there. Since then, No hercnnests have been placed in shorelinetrees there havebeen no activeheron nestsat this site. plantedon privateland. A nest tree at heron colony 8 that historically The number of active great blue heron nests containedmore than 20 neststoppled after 1990. alongthe Reachhas declined from 75 to 34 since To date no herons have nestedin the surviving 1994 (Table I ). The decline has occuned at 6 of fees therc.The number of greatblue herons nesting the l1 coloniesmonitored between 199,1and2001. at colonies2 and 9 appearto haveincreased be- The greatestnumber ofnesting greatblue herons tween1994 and 2001 . Publicaccess to thesecolony occurred at Colony 7. howevet total nests ob- sitesis limited to boat traftic only. servedthcrc each year also steadilydeclined throughoutthe 1990s.The cause(s) ofthe decline Discussion at colony 7 arenot known, but they arenot likely general related to a decline in fledging success(Marco The declinein greatblue heron nests found i 997).Interspecific competition for suitablenesting along the Hanfbrd Reachof the siteswas also notlikely relatedto greatblue heron is not likely ftom reducedfledging successat the nestdeclines at colony 7 becauseno otherpis- coloniesthere. The generaldecline in largetrees civorousavian species such as the black-crowned fbund along the Columbia dver wherepublic ac- night heron (N).dcofar rlctlc'orar), double crested cessis restrictedduring the breedingperiod may cormorxnt (P halu(rocorax auritus) , or gteat egret be the most Jimiting physical characteristicsfbr (Casmerodius.tlbus), have nested there. Vehicle, great blue heron nesting habitat there. The two pedestrian,and boat tratfic occur regularly dur coloniesthat havebeen established on telephone ing the nestingseason near colony 7. Greatblue line towerssupport the premise that natural colony heronnests at colony 10 declinedfiom 16 pairs tlees were limiting resources.The obseNahons in 199,1to 6 in 1995and 1996,and 7 in 1999. alsosuggest these man-made structures can supple This declinecoincided with the lossofa f'ewtrees ment nesting habitat for great blue herons,but at this colony causedby a wild fire during the competitionfor nestingsites with raptorsmay be an issue. Low sub-adult or adult survival and Table L Number of activc grcal blue heron nestsat colonies immigration rates may also be limiting factors :rlong the Hanford Reachofthc Columbia River for nestinggreat blue heronsalong the Hanford 199.1.1995, 1998. 1999, and 2001 Reach of the Columbia River During the mid- 1990smany tagsfrom juveniles and adults were Colonl'. 199,1 1995 1998 1999 t00l retumedto PNNL researchersby staffof theWild- I life ServicesDivision of the Udted StatesDe- 2 partment of Agriculture. Legal shooting of the 3 sub-adultand adult grcat blue herons atthe nearby .l Ringold hatcherysupports the premise that this 5 5 2 sourceof mortality may have contributedto the 6 9 6 6 observedpopulation decline ofgreat herons 1 3l l0 25 2I blue along the Hanlbrd Reachofthe Columbia River. l 7 2 l0 6'/ Acknowledgements t2 performed Tolal 75 69 15 3',7 Work under Contract DE-AC06- 76RL01830with the U.S. DepartmentofEnergy.

Great Blue Herons 359 LiteratureCited Ntarco,J. D. 1997.Factors atTecting great blue heron repro- duction in soulhccnlralWashington. M.S. Thcsis. Geist. D. R. 1995.The :Wh.rt do lre sland to University of . Moscow, Idaho. lose?lllahe I l:ll0- l4l. Rickard,W H. and L. D. Poole. 1989.Terestrial wildlile of Cray. R. H. and w H. Rickard. 1989.The protectedarea of the Hanford Site: Pastand future. Nofh$,est Science Hanlbd as a rclugium ibr nalivc planls and animals. 63r183193. EnvironmentalConservation 16:251-260. Rickard. W H. and K. R. Price. 1989.Tritiun uptake froln Hanson. W C. 1968. Rcccnt history of double-crestedcoF groundrvaterby black locusttrees.Northwest Science morant cok ies in southeastemWashingron. Thc 63:87-89. Murrclct,l9rl5 26. Snodgrass.R. E. 190,1.A list of land birds fron central and souihcancm \\'ashington.The Auk 2l:223-233. Receircd4 Mq' 2002 AccepredJbrpublicqtiott ll Jub- 2003

360 Northwest Science,Vol. 77, No. ,1,2003