Aelred D. Geis, Ph.D.
U.S. Fish and Wildlife Service
Patuxent Wildlife Research Center
Laurel, Maryland 20708
The relative attractiveness of various foods to wild birds at feeding stations was
measured at locations in California, Ohio, Maine and Maryland. Tests were also carried out
near Kansas City, Missouri and in Maryland to better understand how the feeder influences
the species of birds attracted to food. The various bird species differed greatly in
feeding preferences and these preferences were similar at all test locations. Many
commonly used bird foods such as wheat, cracked corn and milo were relatively unattractive
to most wild birds. Also, oil-type sunflower was more attractive than other types of
sunflower seed. The manner of presenting food as well as the kind of food influences the
species attracted to a feeder. For example, chickadees readily use elevated feeders with
small perches. In contrast, juncos prefer the ground or large platforms.
The efficiency with which a specific species can be fed in terms of bird visits per
unit cost can be greatly increased over that resulting from the use of commercial mixes by
presenting attractive food in the manner most effective for the desired species .
This report describes the relative attractiveness of various seeds that were offered to
wild birds at four different locations across the United States. An earlier study (Geis,
1980) in Maryland reported that many commonly used bird foods such as wheat, cracked corn,
and milo were relatively unattractive to most wild birds, while oil-type sunflower was
much superior to the other varieties. The Maryland study also documented striking
differences among bird species in their feeding preferences, suggesting that feeding can
be more selective and economical by presenting specific foods rather than generalized
mixtures. In 1980 over 60 million Americans fed birds, spending over a half billion
dollars for food (Anonymous, 1982). The implications of the Maryland study prompted an
extension of this research over a broader geographic area to determine if the same
relationships existed. Study areas were established in a residential section of Arcadia,
California; at the Allowed Audubon Center and Farm near Dayton, Ohio; and along the coast
of central Maine near Bar Harbor. Studies also were continued at the original location
near Clarksville, Maryland. A concise, popular account of the results of this study has
been published (Geis and Hyde, 1983).
The relative attractiveness of commercially available seeds was measured by presenting
four different seeds simultaneously on experimental feeding tables (122 x 122 cm) divided
into four equal 61 x 61 centimeter compartments (as shown in Fig. 1 of Geis 1980). A
wooden barrier 37 mm high rimmed the outside edge of the table and a 15.2 cm high
Plexiglas partition separated the compartments. A "lantern" type feeder
(Rubbermaid Model #3405) was placed in the center of each compartment. Specific foods
quickly became scattered from the feeders, resulting in each being available throughout
the separate compartments. Bird visits to each compartment were recorded during 30 second
intervals distributed throughout the day. Typically counts were made during 72 intervals
distributed during 15 different five minute periods during the daylight hours. Only birds
attracted to the compartment to feed were recorded. Observations were made throughout the
year since earlier work (Geis, 1980) showed no striking seasonal differences in the
relative attractiveness of foods. After 720 observation intervals usually distributed over
five or more days the positions of the food on the table were changed so that all foods
were presented in all positions. This greatly reduced the possibility of a location bias
influencing the results. When the positions were changed, all spilled food was removed
from each compartment and sorted and cleaned by using screens and blowers. The amount of
uneaten seed was subtracted from the total amount placed in the feeder during the
experiment to measure the food actually taken by the birds. In some instances, data on
food consumption could not be recorded because spillage had spoiled or was eaten by
mammals. Small mammals usually were discouraged from eating the food due either to
difficulty in climbing metal legs or an inability to climb into the feeding table because
the legs were attached some distance from the edge.
Counts were conducted from February 1980 to August 1981 in California; January 1980 to
August 1981 in Maine; February 1980 to August 1981 in Ohio, and January 1980 to March 1982
in Maryland. A total of 710,450 observations were made of birds choosing from among
various types of seed.
Large experimental feeding tables were used because they attracted a wide variety of
species, and they made it possible to more precisely measure the amount of food consumed.
Because the presentation method influences the degree to which various species visit a
feeder, tests were conducted near Kansas City, Missouri and Clarksville, Maryland of three
different feeders and food on the ground. Gray striped, oil-type, black striped and hulled
sunflower were presented both in experimental feeder feeding tables, at tubular feeders
(Droll Yankees, Model B7), and a small, hopper type feeder (Rubbermaid, Model #3405). The
latter two feeders were mounted on poles at the same height as the table. In these tests
the food was simply placed in the compartments of the experimental table with no feeder
Black striped sunflower (BSS) and white proso millet (WPM) provided the standards
against which other foods were compared quantitatively. BSS and WPM were selected as
standards because they are both in common use and virtually all bird species visiting
feeders found one, or the other, or both, relatively attractive. Except for a few
sunflower seed tests both standards were presented with two other kinds of seed in every
experiment. The relative attractiveness of a certain food was determined by dividing the
number of visits to the food by the number of visits to the standard. Thus, relative
attractiveness values of more than 1.0 indicate the candidate food was more attractiveness
than the standard, while those less than 1.0 reflect the extent to which it was less
attractiveness. For example, a relative attractiveness index of 0.5 means that the
candidate was one-half as attractive as the standard. In Table 1 the relative index of
0.01 for canary seed in Ohio, Maryland and Maine indicates that this food received only 1%
as many visits by blue jays (Cyanocitta cristata) in those areas as did BSS.
In contrast, peanut kernels experienced from 50 to 87% more visits.
Results and Discussion
Regional Differences in Bird Feed Preferences
The major reason for collecting data from four widely separated areas was to determine
if there were regional differences in bird feeding preferences. Results from each area
were similar indicating that bird feeding preferences were the same nationwide. Table 1
shows the relative attractiveness of various foods to the blue jay (Cyanocitta cristata)
using BSS as the standard. Peanut kernels were the food preferred by blue jays in all
three areas while gray striped sunflower was consistently more attractive than the
conventional BSS. Note also the remarkably consistent indication that the smaller oil-type
sunflower was about one-fourth as attractive to blue jays as the larger BSS. Buckwheat,
canary seed, flax, all the millets, oats, rice, safflower, sorghum, thistle and wheat were
of low attractiveness in all geographic areas, while fine cracked corn, peanut hearts and
oil-type sunflower were consistently moderately attractive. Chickadees (Table 2) also
demonstrated consistent patterns of feeding preferences between areas. In this table, data
from black-capped chickadees (Parus atricapillus) and Carolina chickadees (Parus
carolinensis) are combined. Observations in Ohio and Maine no doubt were of
black-capped chickadees, while those in Maryland were Carolina chickadees. In all areas,
oil-type sunflower was more attractive to chickadees than BSS seed. Peanut kernels were of
moderate attractiveness, while all other foods except sunflower seeds were consistently
unattractive. Table 3 compares the feeding preferences of cardinals (Cardinalis cardinalis)
in Ohio with those in Maryland, the only locations where this species was present. WPM was
consistently about 20% as attractive as BSS. Results from both also indicated that
oil-type sunflower was about as attractive as BSS. The same general pattern of
attractiveness for different seeds was demonstrated in both Ohio and Maryland.
The house finch (Carpodacus mexicanus) was the only species that was not
consistent in its preferences (Table 4). For this species, data available from California
and Maryland consistently indicated that California house finches were less discriminating
than were those in Maryland. For example, WPM was about half as attractive as BSS in
California, while it was only 6% as attractive in Maryland. Rape seed in California was
28% as attractive, while in Maryland it was only 8%. California house finches also feed
more readily on canary seed, peanut hearts, 4milo and flax. Because house finches only
recently expanded their range into Maryland, it is conceivable that in time they may
develop more diverse feeding habits.
The relative consistency of feeding preferences may also be demonstrated by comparing
the performance of oil-type sunflower with that of BSS for the same species of birds in
different parts of the country (Table 5). If a species prefers oil-type sunflower over BSS
this tendency occurs nation-wide. For example, mourning doves (Zenaida macroura)
consistently prefer oil-type sunflower to BSS. Conversely, blue jays prefer the larger BSS
to oil-type sunflower at all locations. Incidentally, although it is not shown in Table 5,
scrub jays (Aphelocoma coerulescens) in California also preferred the larger
Chi-Square tests of homogeneity were conducted of the data in Tables 1-5 for all foods
(species in Table 5) having a relative attractiveness of more than 0.1 in at least one
area. These tests reflect the likelihood of chance being responsible for the differences
observed. It was found that in a number of instances highly significant differences
occurred in situations where differences were too small to influence decisions concerning
food preferences. For example; in Table 1 both cracked corn and WPM had statistically
highly significant (P<.Ol) differences among areas, yet with the relative
attractiveness of the seed ranging from .11 to .33 for cracked corn and .04 to .15 for
WPM. Thus there was no logical reason to question the conclusion that the attractiveness
of these foods was too low in all areas to use them to attract blue jays. A more
potentially meaningful difference was noted in Table 2 in regard to the attractiveness of
oil-type sunflower to chickadees. In Maryland the relative attractiveness of this food was
substantially higher (4.61) than in Maine (2.17) of Ohio (1.24). However, despite this
difference, there was no reason to reject the conclusion that oil-type sunflower is better
than conventional black stripe as a chickadee food. Except for house finches' tendency to
be less specific in their preferred foods in California than in Maryland, the bird species
studied all showed the same preference patterns in all of the widely distributed areas.
Thus, in general, summaries of feeding preferences obtained by combining data from all
study areas should indicate feeding preferences throughout the United States.
Relative Attractiveness of Various Foods to Birds
The relative attractiveness of various foods to common bird species is summarized in
Table 6 and 7, which pool the data from all four areas. Table 6 presents results when
regular BSS was used as the standard, while in Table 7, WPM was the standard. Note that
each table lists first those bird species that found the standard upon which the table was
based more attractive than the other standard, since better information on the ratings of
various foods is obtained by focusing attention on the results obtained when the most
attractive standard was used. For example, it is better to use BSS to judge the
attractiveness of foods to blue jays since that species found WPM to be only 9% as
attractive as BSS. In contrast, WPM is the best standard for the mourning dove since doves
preferred the millet more than twice as much as regular BSS. The rating of foods compared
with the less attractive standard also is shown in Tables 6 and 7 because some species
readily ate both standards, and even if they didn't, the results confirm the findings from
the more attractive standard. The likelihood that chance variation would cause a
misleading conclusion is very remote in view of the large sample sizes involved. Except
for foods that were rarely eaten (therefore it doesn't make any difference) the confidence
interval around all relative attractiveness index values can easily be determined by
regarding the ratio of visits to the candidate food to total visits (visits to the
candidate plus the standard) as a binomial distribution. This is a reasonable assumption
since the bird had the choice of either visiting the candidate food or the standard, and
the relative attractiveness index value is based on the ratio of visits to one to visits
to the other. Summaries of the various foods' attractiveness follows.
Buckwheat (Fagopyrum esculentum)
Only mourning doves showed interest in buckwheat, and even doves found it only
one-fourth as attractive as WPM.
Canary Seed (Phalaris canariensis)
Canary seed is eaten by the same species that like WPM, but to a somewhat lesser
extent. For example, mourning doves find canary seed 61% as attractive, house sparrows (Passer
domesticus) 50% as attractive, song sparrows (Melospiza melodia) 72%
as attractive as WPM. Since canary seed is more expensive and less attractive than WPM it
is not a good alternative.
Cracked cord (Zea mays)
The results presented in Tables 6 and 7 tend to maximize the attractiveness of cracked
corn because "fine" cracked corn was used. A "coarse" cracked corn, in
limited tests, was found to be substantially less attractive. The birds that found corn
most attractive were the white-throated sparrow (Zonotrichia albicollis),
and the common grackle (Ouiscalus quiscula), both of which found it to be
slightly more than half as attractive as the appropriate standards. Mourning doves and
blue jays also showed some interest in fine cracked corn. In addition to being relatively
unattractive, cracked corn has a tendency to mold and cake up in feeders.
Flax (Linum berlandieri)
Flax was almost completely ignored by all species with two exceptions. Western house
finches found it 36% as attractive as BSS as shown earlier in Table 4. Mourning doves
selected it 11% as often as WPM (Table 7).
German (Golden) Millet (Setaria itabia var stramine ofructa)
This small seed is attractive to the same species that find WPM attractive, but to a
lesser degree. It was an attractive food to small sparrow-like birds and mourning doves.
Doves found German millet to be about 77% as attractive as WPM.
Red Proso Millet (Panicum miliaceum)
This is a different variety of the same species as WPM, however, it is generally less
attractive than WPM. For example, house sparrows visited it 45% as many times as WPM. It
has characteristics similar to WPM and can be used as a substitute when WPM is not
White Proso Millet (Panicum miliaceum)
Because of the general attractiveness of this seed to a variety of birds, it was used
as a standard against which other seeds were compared. Of the species shown in Table 7 for
which this standard was most attractive, namely mourning doves, house sparrows,
brown-headed cowbirds (Molothrus ater), white-crowned sparrows (Zonotrichia leucophrys),
white-throated sparrows and song sparrows. WPM was more attractive than any other food
with the exception of hulled sunflower kernels and pieces, which white-crowned and
white-throated sparrows preferred to WPM.
Oats (Avena sativa)
Both whole oats and hulled oats, commonly called oat groats, were consumed to only a
very limited degree by all species. The common grackle showed the greatest interest in
oats, many 35% as many visits to whole oats as to the preferred BSS. It was noted in the
course of the study that the hulled oats, in addition to being unattractive as food, are
very vulnerable to insect infestation. Of the species not shown in the tables, the
starling (Sternus vulqaris) was the only one that found hulled oats
particularly attractive, preferring it to either WPM or BSS.
Peanuts (Arachis hypogaea)
Both peanut hearts and kernels were tested and proved to have quite different
characteristics. Peanut hearts, which are the embryos of the peanuts removed in making
peanut butter, were attractive only to starlings, which made 95 visits to peanut hearts to
every visit to BSS. Peanut hearts are sometimes added to mixes to make them smell better,
but there is little to recommend them as wild bird food. In contrast, peanut kernels are
uniquely attractive to several species: blue jays, scrub jays and tufted titmice (Parus
bicolor) substantially preferred peanut kernels to BSS. These species also take
sunflower readily, which can be obtained at much lower cost. It is interesting to note
that the species taking peanut kernels had very little interest in peanut hearts. For
example, blue jays found kernels to be 1.6 times more attractive than BSS, while hearts
were taken only 12% as much as BSS.
Rape seed (Brassicanapus)
This seed occasionally appears in "premium" mixes and is a major ingredient
in domestic canary food. For wild birds, however, it was consistently unattractive to all
species. Only mourning doves and house finches were observed taking this food in
significant amounts, and both species found this seed much less attractive than the
Rice (Oryza sativa)
Rice was unattractive to all species. White-crowned sparrows and mourning doves
occasionally took rice, however, they chose it only 14% and 9% as often as WPM.
Safflower (Carthamus tinctor)
Safflower [was initially found to be] relatively unattractive to most bird species.
Only the cardinals and mourning doves showed interest in this food: cardinals found it
about 30% as attractive as BSS, while mourning doves found it about 20% as attractive as
WPM. White throated and song sparrows showed some interest in safflower. Because the
relatively poor performance of safflower seed was contradicted by its apparent popularity,
additional tests were carried out.
Safflower was presented at the Maryland test site between February 13, 1985 and April
17, 1985. During this long period of exposure, there was a gradual increase in the
utilization this seed received from cardinals. During the period from February 13 through
March 2, it was only 23% as attractive as BSS. In contrast, during the period March 29
through April 17 there were actually more visits by cardinals to safflower than to BSS,
yielding a relative attractiveness index of 1.13. White throated sparrows also reflected a
tendency to accept safflower more readily after three months' exposure to it than was
initially the case. Toward the end of the test, safflower was eaten as readily as BSS.
Thus it appears that if presented for a substantial period of time, the safflower will
perform better than shown by the test results presented in Tables 6 and 7. A potential use
of safflower would be to attract cardinals while discouraging most other species.
Milo or Sorghum (Sorghum vulgare)
Three types of sorghum seeds are listed in Tables 4, 6, and 7. The first entry for
"red" is a standard commercial variety of unknown origin. This would be expected
to be typical of the milos available to feed birds. Milo is generally an unattractive food
to all species, a surprising result in view of the popularity it has as an ingredient in
wild bird food mixes. It was most attractive to mourning doves, which found it about 40~
as attractive as WPM. Most of the sorghum produced today is of a "bird
resistant" variety that has been selectively produced to make it unattractive to
birds so that crop depredations can be reduced. This prompted tests comparing the
performance of high tannin, i.e., bird resistant, varieties with low tannin, or non-bird
resistant varieties. These tests indicated that generally the low tannin varieties were
much more attractive to birds than the high tannin varieties. However, even the low tannin
milo was of relatively low attractiveness when compared with either of the standards.
Sunflower Products (Helianthus annuus)
Black Striped Sunflower Seeds
BSS is an extremely popular and effective bird food. The form commercially marketed as
bird feed tends to have relatively small seeds because the BSS crop is screened so that
the larger seeds can be used for human consumption. This is doubly advantageous since the
larger seed is generally less attractive to birds than the smaller seed. The two other
forms of BSS, described below, are also shown in the tables.
Eller is a small form of BSS grown in Georgia for export to Europe. Cardinals, purple
finches (Carpodacus purpureus), house finches, house sparrows and
white-throated sparrows all showed a preference for Eller over the regular BSS, while blue
jays, scrub jays and tufted titmice preferred the larger BSS.
Large Black Striped Sunflower Seeds
Jays and tufted titmice were the only species that preferred this large seed (obtained
Gray Striped Sunflower Seeds
Although this large sunflower seed is visually appealing to people, very few birds
preferred it. Only the species liking large seeds (jays and tufted titmice) found this
form as attractive as BSS. This rather expensive sunflower product can be viewed as an
inferior substitute for BSS.
Hulled Sunflower Pieces and Sunflower Kernels
Whole or broken kernels of hulled sunflowers were very attractive to American
goldfinches (Carduelis tristis) and house finches. They were also readily
taken by some species that prefer WPM to BSS, such as white-crowned and white-throated
sparrows, which took sunflower kernels and pieces more readily than WPM. Sunflower kernels
have the added advantage that their use by birds does not result in the accumulation of
hulls, which some people find objectionable.
Oil-type Sunflower Seeds
The small, black oil-type sunflower seed is superior to other foods, including BSS, for
most bird species. Among the common species visiting feeding tables, only the tufted
titmouse, grackle and blue jay did not demonstrate a preference for oilt ype sunflower
over BSS. Some species that are normally regarded as small-seed eaters took oil-type
sunflower much more readily than BSS. For example, mourning doves found it almost as
attractive as WPM, while both white-throated and song sparrows took it readily. Shortly
after the conclusion of the major portion of this study of nation-wide tests, oil-type
sunflower that was substantially smaller than that used in the tests became commercially
When the reaction of birds to this smaller seed was compared with that to the seed used
in earlier tests, the smaller seed was found to be far more attractive for several
species, especially American goldfinches (Table 8). This information suggests that the
superior performance of oil-type sunflower would have been even better had smaller seed
been used. Incidentally, the smaller seed is viewed by the sunflower industry as
"inferior" and is less expensive than the "higher" quality seed.
Oil-type sunflower seeds tend to last longer in bird feeders because of the greater number
of seeds per unit weight. There are from two to four times as many oil-type sunflower
seeds as BSS in the same weight. The difference is particularly important when one
considers the number of seeds found in a 50 pound bag of bird seed. A bag of the small
oil-type sunflower seed contains over 600,000 seeds while conventional BSS has about
179,000 seeds per 50 pound bag.
Niger (Guizotyia absyssinica)
Niger (also called thistle seed) was very attractive to goldfinches. It was generally
unattractive to all other species, with the exception of mourning doves and house finches.
This food is especially effective when presented in the summer in tubular feeders, to
attract goldfinches at a time when their plumage is especially beautiful.
Wheat (Triticum aestivum)
A number of bird species eat wheat, but none find it nearly as attractive as WPM or
BSS. Among the common visitors to feeding stations, mourning doves, house sparrows and
white-throated sparrows all find wheat to be about one-fifth as attractive as WPM. The
general unattractiveness of wheat to most bird species may be used to attract mourning
doves while avoiding disturbance by other species (Reeves, Geis and Kniffen 1968).
However, this general unattractiveness makes it an ineffective ingredient when included as
it commonly is in wild bird food mixes.
Preferred Foods of Various Bird Species
The most attractive foods for a variety of bird species are summarized in Table 9.
Foods are listed in order of attractiveness. You will note there are more species entered
here than are found in Tables 6 and 7. This is because it is easier.to identify preferred
foods than it is to also categorize the extent to which other foods are unattractive. Note
that starlings find only peanut hearts and hulled oats relatively attractive.
Effect of Type of Feeder on Feeding Activity
The data presented up to this point have been based on observations of large
experimental feeding tables. Because of obvious differences in feeding habits, it could be
expected that birds would be influenced by not only the food presented, but by the type of
feeder used. This is demonstrated in Tables 10, 11, 12 and 13, which show the species
composition of birds attracted to the same sunflower products presented in four different
feeding situations in Missouri and three different feeders in Maryland. In each instance,
the same food is presented in each feeder. Note, for example, the consistent tendency of
house sparrows and cardinals to use the table more than the other feeders. Perhaps the
most striking difference is demonstrated by the dark-eyed junco (Junco hyemalis)
which utilized the food on the ground, but rarely appeared on any of the elevated feeders.
This tendency to avoid small, elevated feeders was demonstrated in Maryland, where juncos
tended to use the table more than the smaller feeders. Chickadees consistently utilized
the small, elevated feeders more than the tables or the ground. Despite differences in the
types of feeders favored by the various species the overall influence of type of food was
still evident. Note, for example, the consistently higher percentage of American
goldfinches appearing at hulled sunflower seeds than was the case for other foods. Thus,
the kind of birds visiting a feeding situation is influenced both by the kind of food
used, and also by the type of feeder in which it is presented.
General Conclusions and Recommendations
Decisions concerning the best foods to use depend upon the attractiveness of the foods
to the desired bird species in relation to cost. An important benefit of the inclusion of
relatively unattractive ingredients in many commercial wild bird food mixes is that they
greatly reduce the cost of feeding. Not only is the initial cost low, the overall cost is
as well because the food is taken at a low rate. The relative costs of different foods
were presented in Geis (1980) Special Scientific Report #233 and have generally remained
Because of their general attractiveness, oil-type sunflower seed and WPM should play a
prominent part in most feeding programs. Although BSS, which has traditionally been used,
is an excellent bird food, the oil-type sunflower seed is more attractive to most species
and is no more expensive. People wanting to maximize bird feeding activity should avoid
the use of commercial mixes which typically contain generally unattractive foods such as
wheat, milo, peanut hearts, hulled oats and rice. However, because the species composition
of the birds present varies from time to time and also from place to place, it is
impossible to recommend what would constitute the appropriate ratio of even attractive
ingredients. Therefore, it is not possible to formulate an entirely satisfactory seed
mixture. The present study suggests that the best over-all results can be obtained by
purchasing oil-type sunflower seed and WPM and offering them separately. This technique
also facilitates recognition of the differences in feeding behavior among the various
species. Specifically, those species that prefer WPM tend to use the ground or large
platform feeders, while many species taking oil-type sunflower seed readily use elevated
feeders with small perching areas such as tubular feeders. The present research
establishes that the results of earlier studies applies throughout the United States and
that the efficiency with which wild birds are fed could be improved by recognizing the
great differences among bird species in the specific foods they find attractive and the
manner in which they prefer to eat. This information on feeding preferences and behavior
can be used to present foods known to be attractive in the amounts and ways that are most
efficient for the desired bird species present.
Bibliographic Card Summary
The relative attractiveness of various foods to wild birds at feeding stations was
measured in five locations throughout the United States to better understand how the kind
of food and type of feeder influences the number and species of birds attracted. These
tests indicated that various species differed greatly in feeding preferences and these
preferences were similar at all test locations. Some commonly used food such as cracked
corn, milo and wheat were relatively unattractive to most wild birds, while oil-type
sunflower and white proso millet were generally attractive. The manner of presenting food
as well as the kind of food influenced the species attracted to feeders. Key words: Bird
food, sunflower, white proso millet, artificial bird feeders, and bird food
This study could not have been carried out without the excellent cooperation of the
people who actually made the bird counts in a careful, highly controlled manner. In
California, counts were made by Mrs. Merle Froke, in Ohio by Mrs. Diana Ullery, and in
Maine by Mrs. Maude Russell. In Missouri, Mr. Harold Burgess made the counts at the Martha
LaFeet Thompson Nature Sanctuary. By far the largest volume of data was collected near
Clarksville by Mrs. Leitha Geis, who contributed to all aspects of this study.
Administrative arrangements for studies in California, Ohio and Maine were made through a
contact with the Urban Wildlife Research Center.
Geis, Aelred D. 1980. Relative Attractiveness of Different Foods at Wild Bird Feeders.
U.S. Fish & Wildlife Service Special Scientific Report No. 233. 11 pp.
Geis, Aelred D. and Donald B. Hyde, Jr. 1983. Wild Bird Feeding Preferences.
National Wildlife Federation, Wash., D.C. 6 pp.
Reeves, Henry M., Aelred D. Geis and F. Charles Kniffen. 1968. Mourning Dove Capture
U.S. Fish & Wildlife Service Special Scientific Report No. 117. 63 pp.
Anonymous. 1982. 1980 National Survey of Fishing, Hunting, and Wildlife-Associated
U.S. Fish & Wildlife Service. 156 pp.