Gray Jays (Perisoreus canadensis) read ily learn that humans can be excellent sources of food (e.g. Rutter 1969) and therefore are common in many picnic areas, campgrounds and other areas frequented by humans in the Rocky Mountains. Bes ides rapid recognition of humans as sou rces of food, Gray Jays also do not appear to readily forget a discovered food source (e.g. Rutter 1969). Gray Jays also optimize food selection on the bas is of caloric intake and the effort required to identify and handle the food items (Maccarone and Montevecchi 1986) aga in, making places such as picnic areas, campgrounds and other human-frequented areas optimal places to forage

Engeman, R. M.

Wiloth, C. J.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff Publications U.S. Department of Agriculture: Animal and Plant Health Inspection Service 2014 Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal Aquatic Food Source R. M. Engeman USDA-APHIS-Wildlife Services, s_r100@yahoo.com C. J. Wiloth Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc  Part of the Life Sciences Commons Engeman, R. M. and Wiloth, C. J., "Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal Aquatic Food Source" (2014). USDA National Wildlife Research Center - Staff Publications. 1494. https://digitalcommons.unl.edu/icwdm_usdanwrc/1494 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal Aquatic Food Source R. M. Engeman and C. J. Wiloth Gray Jays (Perisoreus canadensis) read ily learn that humans can be excellent sources of food (e.g. Rutter 1969) and therefore are com-mon in many picnic areas, campgrounds and other areas frequented by humans in the Rocky Mountains. Bes ides rapid recognition of hu-mans as sources of food, Gray Jays also do not appear to readily forget a discovered food source (e.g. Rutter 1969). G ray Jays also optimize food selection on the bas is of ca loric intake and the effort required to identify and hand le the food items (Maccarone and Montevecchi 1986) aga in, making places such as picnic areas, campgrounds and other human-frequented areas optimal places to forage. Such is the case at the Sprague Lake picnic area in Rocky Moun-tain Nationa l Park, Colorado. This is a popular and frequented picnic site where Gray Jays are abundant and bold in seeking human food. As its name implies, this picnic ground is located near Sprague Lake, with the lake's inlet stream running adjacent to the picnic ground. It is here that we observed Gray Jays conditioning to another human-enabled, but aquatic, food source. Fig. 1. A Gray Jay /Jicks u/J eggs released from a female brook trout when handled by a fisherman for hook removal in October 2010. Photo by C. Wi loth Colorado Birds Summer 20 14 Vo l. 48 No.3 227 During the fall there is a spawn run of non-native brook trout (Salvelinus iontinalis) from Sprague Lake into the inlet creek bes ide the picnic ground. At this time the spawning fish are targeted and readily caught by fi shermen. Many of the ripe females are bulging with eggs and often release va rying amounts of eggs when handled by fishermen for hook removal or even just through struggling at the end of the line. G ray Jays apparently have learned these eggs are a food source and have developed the behav ior of follow ing fishermen, or wa it ing nearby a fi sherman, and then qu ickly mov ing in to pick up eggs when re leased from a captured fish. We first observed this behav ior in October 201 0 (Fig. 1) and we subsequently observed it during the brook trout spawn runs in 2011 and 2012 (Fig. 2). Given the Gray Jay's quick recognition of a novel food source, that the Gray Jays around the picnic area are a lready condit ioned to seeking food fro m humans and that Gray Jays optimize forag ing according to ef-fort and ca loric intake, it is not surprising that they learned to fo llow fishermen as an effic ient means to scavenge a nutritious protein-rich food source that otherwise would not be available to them. We also observed other birds consuming brook trout eggs during the spawn runs from 2010 - 2012. The stream sections where many of the spawning redds (nests) are located are very clear and shallow (often only 15-25 cm in depth) making it easy to observe Mallards (An as plat),rhynchos ) and American Dippers (Cincius mexicanus) for-aging in the redds. Yet only the Gray Jays appear conditioned to fo l-low fi sherman in wa it of a fi sh egg reward. This behav ior can only occur during the fall brook trout spawn run as there are no spring or summer spawning species at Sprague Lake. The situation , not unexpectedly, was much different in 2013. A visit to Sprague Lake on 2 Sept. 2013 showed the vanguard of the brook trout spawn run entering the stream, but actual spawning ac-tivity had not yet begun. During the week beginning 9 Sept. , the Es-tes Park/Rocky Mountain National Park area experienced consecu-tive days of heavy rains leading to significant fl ood ing on all streams reg ionally. Floods destroyed the primary access routes to Rocky Mounta in Park. Subsequent to the flood damage, the park was closed for nearly two weeks in early Oct. due to a lapse government fund-ing. Observations at Sprague Lake were again made on 18 Oct. The stream had obvious impacts from the flooding, but a large number of brook trout were in the stream and spawning. Undoubtedly, the flooding had scoured the stream of an y eggs laid prior to the rains and probably delayed spawning fi sh from entering the stream. The flood effects coupled with the park closure meant that the Sprague Lake picnic area had few if any visitors. Thus, the attract ion to anthro-228 Colorado Birds Summer 20 14 Vol. 48 No.3 pogenic food sources at the picnic ground vanished, including trout eggs released during the capture of spawning brook trout. No Gray Jays were obse rved during the brief visit to the picnic ground nor were they seen in conjunction with the lone fisherman at the stream, a lthough captured female trout were releasing eggs when handled for hook release. Dried eggs from a previous day were observed on the bank, something never observed in the three previous years, as Gray Jays, or possibly other animals would rapidly consume them. Another visit to the location was made on 14 Nov. 2013. There were only a few spawning brook trout remaining and just one fi sherman was pres-ent and no Gray Jays were observed. It will be interest ing to observe the behavior of Gray Jays during the 2014 spawn run to see if they once aga in fo llow fishermen, opportunistica lly feeding on trout eggs. LITERATURE CITED Rutter, R. J. (1969). "A contribution to the biology of the G rey Jay (PerisoreLls canaden-sis)". Canad ian Field-Naturalist 83 (4): 300-3 16 Maccarone, A. D.; Montevecchi, W. A. (1986). "Factors affect ing food choice by Gray Jays" . Bird Behavior 6 (2): 90-92 R. M. Engeman, USDA/APHIS/Wildlife Services/National Wildlife Research Center, 4101 LaPorte Ave., Fort Collins, CO 80521-2154 c. J. Wiloth, 485 Pelican Cove, Windsor, CO 80550 Fig. 2. A Gray Jay holds a brook trout egg in its mouth after being released from a female brook trout when handled by a fisherman for hook removal in November 2012. Photo by R. Engeman Colorado Birds Summer 20 14 Vo l. 48 No.3 229 

Anthropogenic Conditioning
of Gray Jays to a Nutritious,
Seasonal Aquatic Food Source

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
USDA National Wildlife Research Center - Staff 
Publications 
U.S. Department of Agriculture: Animal and 
Plant Health Inspection Service 
2014 
Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal 
Aquatic Food Source 
R. M. Engeman 
USDA-APHIS-Wildlife Services, s_r100@yahoo.com 
C. J. Wiloth 
Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc 
 Part of the Life Sciences Commons 
Engeman, R. M. and Wiloth, C. J., "Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal 
Aquatic Food Source" (2014). USDA National Wildlife Research Center - Staff Publications. 1494. 
https://digitalcommons.unl.edu/icwdm_usdanwrc/1494 
This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant 
Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion 
in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of 
DigitalCommons@University of Nebraska - Lincoln. 
Anthropogenic Conditioning 
of Gray Jays to a Nutritious, 
Seasonal Aquatic Food Source 
R. M. Engeman and C. J. Wiloth 
Gray Jays (Perisoreus canadensis) read ily learn that humans can be 
excellent sources of food (e.g. Rutter 1969) and therefore are com-
mon in many picnic areas, campgrounds and other areas frequented 
by humans in the Rocky Mountains. Bes ides rapid recognition of hu-
mans as sources of food, Gray Jays also do not appear to readily forget 
a discovered food source (e.g. Rutter 1969). G ray Jays also optimize 
food selection on the bas is of ca loric intake and the effort required 
to identify and hand le the food items (Maccarone and Montevecchi 
1986) aga in, making places such as picnic areas, campgrounds and 
other human-frequented areas optimal places to forage. 
Such is the case at the Sprague Lake picnic area in Rocky Moun-
tain Nationa l Park, Colorado. This is a popular and frequented picnic 
site where Gray Jays are abundant and bold in seeking human food. 
As its name implies, this picnic ground is located near Sprague Lake, 
with the lake's inlet stream running adjacent to the picnic ground. It 
is here that we observed Gray Jays conditioning to another human-
enabled, but aquatic, food source. 
Fig. 1. A Gray Jay /Jicks u/J eggs released from a female brook trout when handled by 
a fisherman for hook removal in October 2010. Photo by C. Wi loth 
Colorado Birds Summer 20 14 Vo l. 48 No.3 227 
During the fall there is a spawn run of non-native brook trout 
(Salvelinus iontinalis) from Sprague Lake into the inlet creek bes ide 
the picnic ground. At this time the spawning fish are targeted and 
readily caught by fi shermen. Many of the ripe females are bulging 
with eggs and often release va rying amounts of eggs when handled 
by fishermen for hook removal or even just through struggling at the 
end of the line. G ray Jays apparently have learned these eggs are a 
food source and have developed the behav ior of follow ing fishermen, 
or wa it ing nearby a fi sherman, and then qu ickly mov ing in to pick 
up eggs when re leased from a captured fish. We first observed this 
behav ior in October 201 0 (Fig. 1) and we subsequently observed it 
during the brook trout spawn runs in 2011 and 2012 (Fig. 2). Given 
the Gray Jay's quick recognition of a novel food source, that the Gray 
Jays around the picnic area are a lready condit ioned to seeking food 
fro m humans and that Gray Jays optimize forag ing according to ef-
fort and ca loric intake, it is not surprising that they learned to fo llow 
fishermen as an effic ient means to scavenge a nutritious protein-rich 
food source that otherwise would not be available to them. 
We also observed other birds consuming brook trout eggs during 
the spawn runs from 2010 - 2012. The stream sections where many 
of the spawning redds (nests) are located are very clear and shallow 
(often only 15-25 cm in depth) making it easy to observe Mallards 
(An as plat),rhynchos ) and American Dippers (Cincius mexicanus) for-
aging in the redds. Yet only the Gray Jays appear conditioned to fo l-
low fi sherman in wa it of a fi sh egg reward. This behav ior can only 
occur during the fall brook trout spawn run as there are no spring or 
summer spawning species at Sprague Lake. 
The situation , not unexpectedly, was much different in 2013. A 
visit to Sprague Lake on 2 Sept. 2013 showed the vanguard of the 
brook trout spawn run entering the stream, but actual spawning ac-
tivity had not yet begun. During the week beginning 9 Sept. , the Es-
tes Park/Rocky Mountain National Park area experienced consecu-
tive days of heavy rains leading to significant fl ood ing on all streams 
reg ionally. Floods destroyed the primary access routes to Rocky 
Mounta in Park. Subsequent to the flood damage, the park was closed 
for nearly two weeks in early Oct. due to a lapse government fund-
ing. Observations at Sprague Lake were again made on 18 Oct. The 
stream had obvious impacts from the flooding, but a large number 
of brook trout were in the stream and spawning. Undoubtedly, the 
flooding had scoured the stream of an y eggs laid prior to the rains and 
probably delayed spawning fi sh from entering the stream. The flood 
effects coupled with the park closure meant that the Sprague Lake 
picnic area had few if any visitors. Thus, the attract ion to anthro-
228 Colorado Birds Summer 20 14 Vol. 48 No.3 
pogenic food sources at the picnic ground vanished, including trout 
eggs released during the capture of spawning brook trout. No Gray 
Jays were obse rved during the brief visit to the picnic ground nor 
were they seen in conjunction with the lone fisherman at the stream, 
a lthough captured female trout were releasing eggs when handled for 
hook release. Dried eggs from a previous day were observed on the 
bank, something never observed in the three previous years, as Gray 
Jays, or possibly other animals would rapidly consume them. Another 
visit to the location was made on 14 Nov. 2013. There were only a 
few spawning brook trout remaining and just one fi sherman was pres-
ent and no Gray Jays were observed. It will be interest ing to observe 
the behavior of Gray Jays during the 2014 spawn run to see if they 
once aga in fo llow fishermen, opportunistica lly feeding on trout eggs. 
LITERATURE CITED 
Rutter, R. J. (1969). "A contribution to the biology of the G rey Jay (PerisoreLls canaden-
sis)". Canad ian Field-Naturalist 83 (4): 300-3 16 
Maccarone, A. D.; Montevecchi, W. A. (1986). "Factors affect ing food choice by Gray 
Jays" . Bird Behavior 6 (2): 90-92 
R. M. Engeman, USDA/APHIS/Wildlife Services/National Wildlife Research Center, 
4101 LaPorte Ave., Fort Collins, CO 80521-2154 
c. J. Wiloth, 485 Pelican Cove, Windsor, CO 80550 
Fig. 2. A Gray Jay holds a brook trout egg in its mouth after being released from a 
female brook trout when handled by a fisherman for hook removal in November 2012. 
Photo by R. Engeman 
Colorado Birds Summer 20 14 Vo l. 48 No.3 229 


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Anthropogenic Conditioning of Gray Jays to a Nutritious, Seasonal Aquatic Food Source

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