Floor laying by Pekin ducks: Effects of nest box ratio and design
M. M. Makagon*†1 and J. A. Mench†‡2
*Animal Behavior Graduate Group, †Department of Animal Science, and ‡Center for Animal Welfare,
University of California, Davis, One Shields Avenue, Davis 95616
ABSTRACT The laying of eggs outside nest boxes is a
common problem in poultry production systems. Factors potentially contributing to floor laying by Pekin
ducks were investigated. In a 2 × 2 factorial design, 16
groups of 18-wk-old ducks (8/group) were provided access to either 2 (4 ducks/box) or 8 (1 duck/box) closedtopped or open-topped nest boxes. Egg locations were
recorded daily for 16 wk. Video analyses were used to
determine the time of day eggs were laid on the floor
when the ducks were 18 to 22, 26, 30, and 34 wk of age.
An analysis of nontoxic dye deposition in the egg yolk
was conducted on wk 30, 32, and 36 to determine the
contribution of each duck to floor laying. The proportion of floor eggs was especially high early in the laying
cycle, reaching 84 and 44% of eggs laid in pens offering ratios of 4 ducks/box and 1 duck/box, respectively, when ducks were 22 wk of age. Repeated measures
ANOVA revealed that although the proportion of floor
eggs decreased over time (F3,9 = 29.29, P < 0.0001), it
remained greater in the groups housed with 4 ducks/
box vs. 1 duck/box (F1,11 = 24.09, P = 0.0005). The
proportion of floor eggs was not affected by box design
(F1,11 = 0.08, P = 0.8). Not all available nest boxes
contained eggs on a given day, and the distribution of
eggs within the pen was clumped. However, it was unlikely that this reflected nest box location preferences
because the locations of the eggs laid within the nest
boxes changed over time. Taken together, these results
suggest that floor laying by Pekin ducks may be caused
in part by insufficient nest box availability. However,
the clumped distribution of eggs suggests that other
social factors, such as conspecific attraction, may also
be important.
Key words: nest choice, domestic duck, floor egg
2011 Poultry Science 90:1179–1184
doi:10.3382/ps.2010-01287
INTRODUCTION
Floor laying, which is the laying of eggs outside designated nest boxes, is a common problem in poultry
breeding and laying systems. Floor-laid eggs are dirtier, have higher bacterial counts, have more cracks and
breaks, and require longer collection times than eggs
laid within nest boxes. As a result, floor eggs are associated with comparatively lower quality grades, lower
hatchability, and increased production costs (RietveldPiepers et al., 1985). To reduce the floor-laying problem in commercial flocks effectively, it is important to
understand factors governing nest site selection. Several studies have assessed factors influencing nest site
selection by commercial chickens, but far less is known
about nesting choices of other poultry species, including Pekin ducks.
©2011 Poultry Science Association Inc.
Received December 8, 2010.
Accepted February 22, 2011.
1 Present address: Department of Animal Science, Michigan State
University, 3270J Anthony Hall, East Lansing, MI 48824.
2 Corresponding author: [email protected]
Nest box competition is thought to contribute to
floor laying by chickens (Kite et al., 1980). Such competition could account for the high level of floor laying
(up to 40% during the early stages of lay; Cherry and
Morris, 2008) observed on commercial duck farms. In
the United States, commercially housed breeder ducks
are raised with access to wooden nest boxes. One nest
box is typically provided for every 4 to 5 hens. Because
nesting behaviors of flock members are likely clumped
in time, high duck-to-nest box ratios could lead to nest
box competition. Floor laying may therefore reflect the
behavior of ducks that are unable to compete successfully for nest box access and are instead forced to lay
on the pen floor. Decreasing the duck-to-nest box ratio
could reduce nest box competition and floor laying.
Increasing the enclosure level of nest boxes could also
decrease the frequency of floor laying. Although evidence as to whether nest box enclosure plays an important role in nest site selection by chickens is equivocal
(Kite et al., 1980; Sherwin and Nicol, 1992), nest concealment is considered to be a primary factor affecting
the nest choices of wild Mallard ducks (Bjarvall, 1970),
from which Pekins were domesticated. Additionally,
previous research has shown that when given a choice
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Figure 1. Photos of a) open-top and b) closed-top nest boxes. Ducks in each pen received only 1 nest box type. The open-top nest boxes
resembled those typically used by the US duck industry.
of various nest box types, Pekin ducks prefer to lay in
those offering the highest levels of enclosure (Makagon
et al., 2011). Commercial breeder ducks are typically
provided with nest boxes that feature only a limited
amount of enclosure. Providing ducks with nest boxes offering a higher degree of enclosure could increase
their attractiveness and lead to a reduction in floor laying among the flock.
Approaches to managing floor laying may depend on
whether the floor laying is widespread or can be attributed to the behavior of particular birds. For example,
most commercial chickens lay the majority of their eggs
within designated nest boxes, whereas others floor lay
regularly (Kite et al., 1980). Understanding whether
ducks can similarly be characterized as either floor or
nest users could be useful for identifying and selecting for characteristics that correlate with nest use to
decrease floor laying. This study examined individual
variation in floor-laying patterns among Pekin ducks,
and evaluated the effects of duck-to-nest box ratio and
nest box enclosure on the frequency of floor laying.
(OP) or a closed-top (CL) design were placed in each
of the 16 treatment pens. The OP boxes featured 0.4 ×
0.4 m back and side panels and a short 0.15 × 0.4 m
front panel, and were similar in design to those used by
commercial Pekin breeders. The CL boxes were modified from OP boxes by the addition of a flat roof. Figures 1 and 2 depict nest box designs and the placement
of nest boxes within pens. Solid tarpaulins were used to
provide visual isolation between pens.
Bird Husbandry
All flock management and husbandry practices were
based on industry recommendations and the Guide for
the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 1999), and were
approved, along with experimental procedures, by the
University of California, Davis, Institutional Animal
MATERIALS AND METHODS
Subjects and Treatment Groups
The 128 ducks used in this experiment were selected
from a flock of 168 female ducklings used in a series of
studies on Pekin duck nesting behavior. The day-old
ducklings were obtained from a commercial hatchery
and placed in an experimental facility in 3.0 × 3.0 m
floor pens in 4 groups of approximately 40. At 6 wk
of age, the ducklings were distributed among 8 such
rearing pens to prevent overcrowding. The ducks remained in these groups until 15 wk of age. One duck
from each rearing pen was then moved into each of
16 treatment pens measuring 3 × 1.5 m, forming 16
groups of 8 ducks. Two wk later, 4 groups of ducks
were assigned to each of 4 treatment groups. In a 2
× 2 factorial arrangement either 2 (4 ducks/box) or 8
(1 duck/box) particle board nest boxes of an open-top
Figure 2. Diagram of the arrangement of nest boxes within the
pens containing a) 8 and b) 2 nest boxes. Pens were 3.0 × 1.5 m and
contained 2 or 8 nest boxes of an open-topped or a closed-topped design. Drinkers were placed against the far end of the pen; nest boxes
were placed closer to the pen aisle. The position of nest boxes against
the right vs. left walls of the pen was counterbalanced within treatments.
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FLOOR LAYING BY PEKIN DUCKS
Care and Use Committee. Wood shavings, which covered the pen floors and served as nesting material, were
changed weekly. Ducks had constant access to water via
nipple drinkers and were limit-fed a commercial diet.
They were initially scatter-fed, but this was discontinued at 16 wk of age when poultry feeders were introduced. There was 5.24 cm of feeder space per bird. Feeders were placed in pens at approximately 0900 h each
morning. The time of feeder removal was based initially
on average BW and later on average egg weight, but it
typically occurred between 1530 and 1630 h.
The ducklings were provided with 24 h of fluorescent
light during the first day. A step-down photoschedule
was then used to decrease the light period by 1 h/d
until an 18L:6D photoperiod was reached. Lights came
on at 0300 h and turned off at 2100 h daily. Artificial
lighting was supplemented by natural lighting, which
entered the house through windows. Temperature in
the house varied with time of day and season. Swamp
coolers and gas hover brooders were used as needed to
help keep the temperature in the house below 27°C during the summer and above 5°C during the winter.
Data Collection
Data on the locations of eggs laid within the pens
and on nest-oriented behaviors (see below) were collected for 16 wk following the introduction of nest boxes, beginning at 18 wk of age. Ducks were individually
marked using nontoxic livestock crayons (All-Weather
Paintstik, LA-CO Industries Inc., Elk Grove Village,
IL) to facilitate individual identification. Eggs were collected daily at the time of feeding and feed removal,
and their weights and locations within the pens (nest
box number or floor) were recorded. Laying locations
of individual ducks were determined using yolk staining
methods modified from Riddle (1910). Following the
method suggested by Appleby and McRae (1983) for
identifying eggs laid by all members of each group simultaneously, multiple ducks in each pen were initially
fed size 0 gelatin capsules (Single “0” Gelatin Caps,
NOW Foods, Bloomingdale, IL) filled with different
doses (75 or 200 mg) of the same dye (Sudan Black B,
Sudan III, or Oil Red O) or a 1:1 mixture of the 2 Sudan dyes (Sigma Aldrich, Saint Louis, MO). Although
egg yolks stained by different colored dyes could be
easily distinguished, it was not possible to discriminate
reliably between egg yolks stained by different doses of
the same dye. However, successful identification of the
laying locations of 127 of the 128 experimental ducks
was achieved when the ducks were 30, 32, and 34 wk
of age by feeding them 1 of 8 different combinations
of dyes (75 mg each) on 2 successive days. Eggs that
were collected on d 2 through 5 after dye feeding were
marked for later identification, hard boiled, and sliced
open to reveal the unique dye patterns. This technique
produced egg yolks containing 1 (if a dye and empty
gelatin capsule were fed) or 2 (if dyes were fed on both
days) colored rings.
Bullet cameras (Speco CVC627B, SPeco Technologies, Amityville, NY) hung from the ceiling were positioned approximately 1.5 m away from the front end of
each pen to provide an overhead view of the entire pen,
including nest boxes and drinker lines. The video image was stored using a ClearVision DVR system (CVDVR1480-16R, Inter-Pacific Inc., Wheeling, IL). The
times of floor-laying events and the locations (floor or
nest box) of all ducks within the pen were determined
based on video recordings taken on 4 consecutive days
per week at 18 to 22, 26, 30, and 34 wk of age.
Statistical Analysis
All statistical analyses were conducting using SAS
statistical software (version 9.2, SAS Institute, Cary,
NC). A 2-way repeated measures ANOVA on the average proportions of floor eggs found in the pens was
conducted using the PROC GLM procedure to assess changes in floor laying over time and the main
effects of duck-to-box ratio (4 ducks/box vs. 1 duck/
box) and nest box design (OP vs. CL), and all interactions among these factors. The analysis focused on
eggs found in each pen at 4, 8, 12, and 16 wk after nest
box introduction, when ducks were 22, 26, 30, and 34
wk old, respectively. The multivariate model was used
for the analysis because the data failed to meet the
sphericity assumption. To examine whether changes in
available floor space accounted for differences in proportions of floor eggs laid in pens with 4 ducks/box vs.
1 duck/box, a repeated measures ANOVA examined
the effect of duck-to-nest box ratio on the proportion
of floor eggs found per available floor space. Binomial
and chi-squared goodness of fit tests were used to compare the distribution of eggs among the available nest
boxes in pens containing 4 ducks/box and 1 duck/box,
respectively. Average laying location consistencies for
ducks housed with 4 ducks/box vs. 1 duck/box were
compared using Student’s t-test.
RESULTS
The locations where 8,911 eggs were laid were recorded over the 16-wk study period. Of these, 2,217 eggs
were found on the floor and 6,694 were found within
nest boxes. In 14 of the 16 pens, the first egg found was
found on the floor.
The proportion of floor eggs decreased with time
(F3,9 = 29.29, P < 0.0001; Figure 3). The main effect
of duck-to-box ratio was significant (F1,11 = 24.09, P
< 0.001), with the proportion of floor eggs greater in
pens with 4 ducks/box than in pens with 1 duck/box.
This effect remained significant even after accounting
for the reduction in available floor space caused by the
placement of an additional 6 nest boxes in the 1 duck/
box treatment pens (F1,11 = 7.10, P = 0.02). Nest box
design did not significantly affect the mean proportion of floor eggs (F1,11 = 0.08, P = 0.78). There were
no significant interactions [design × duck-to-box ratio
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Makagon and Mench
Figure 3. Mean (±SE) proportion of floor eggs collected per treatment at 4, 8, 12, and 16 wk after nest boxes were placed in pens.
Treatment names describe the duck-to-box ratio and type of boxes
made available to ducks in each pen: 1:1 closed-top, 1:1 open-top, 4:1
closed-top, 4:1 open-top.
(F1,11 = 0.20, P = 0.67); duck-to-box ratio × time (F3,9
= 2.75, P = 0.11); design × time (F3,9 = 0.50, P =
0.69); design × duck-to-box ratio × time (F3,9 = 2.74,
P = 0.11)].
Although ducks in each pen laid eggs in all nest boxes over the course of the study, not all of the boxes
were used each day (Figure 4). In pens containing 2
OP boxes (4 ducks/box), the majority of eggs, 55% (P
< 0.001), were found in nest boxes closest to the aisle
(Figure 2b). No differences were found in the distribution of eggs among nest boxes in pens with 2 CL boxes
(P = 0.96). In pens containing 8 nest boxes (1 duck/
box), the distribution of eggs differed from chance
(12.5%) regardless of whether OP (χ27, 2,027 = 353.35,
P < 0.0001) or CL (χ27, 1,900 = 70.91, P < 0.0001) boxes were provided. However, there were no clear trends
for laying in particular nest box positions across the
treatment groups.
Yolk stain analyses enabled identification of the location of at least 3 and up to 11 (mode = 10) eggs laid
by 127 of the 128 ducks. These data reflected eggs laid
on up to 4 consecutive days per week when the ducks
were 30, 32, and 36 wk of age. Occasionally, multiple
eggs were linked to a single duck in one day. Typically, no eggs were identified as laid by that duck on
the previous day, suggesting that the ducks took longer
to produce some eggs. However, to be conservative in
case some eggs had been misidentified, these eggs were
excluded from the analysis. The resulting 1,138 eggs,
including 204 floor eggs, laid by 127 ducks were used
in analyses of individual nesting preferences (Figure 5).
Overall, 45% of ducks laid their eggs exclusively in the
nest boxes. The remaining 55% of ducks laid eggs on
the floor at least occasionally, although none of the
ducks laid 100% of the eggs on the floor. Only 5% (7 of
127 hens) of the ducks could be classified as consistent
floor layers based on the criterion of Riedvelt-Piepers et
al. (1985), which is that the individual lays at least 70%
of its eggs on the floor. Average weekly laying location consistencies, defined as the percentage of eggs laid
in a single location (a specific nest box or the floor),
were determined for 119 ducks whose nesting locations
could be identified on 3 or 4 consecutive days per week.
Ducks housed in pens with 1 duck/box were more consistent in their choice of laying locations (80% ± 2%)
than were ducks housed in pens with 4 ducks/box (69%
± 2%; T1,117 = 3.2, P = 0.002).
Of the 202 floor eggs identified on video, 65% were
laid in the 4 h after the lights went on (0300 to 0700 h),
which corresponded to the time of highest nest box use.
However, 32% were laid during the dark phase (2100 to
0300 h), when nest box activity was low, and 1% were
laid in the afternoon. The remaining 2% of floor eggs
were actually not laid on the floor but were ejected
from nest boxes by the ducks.
Figure 4. Average percentage of observations (days per pen) during which a) 1 to 2 of the available 2 nest boxes in the 4 ducks/box treatment
groups and b) 1 to 8 of the available 8 nest boxes in the 1 duck/box treatment groups contained eggs.
FLOOR LAYING BY PEKIN DUCKS
Figure 5. The average percentage of ducks housed in pens with 4
ducks/box and 1 duck/box laying between 0 and 100% of their eggs on
the pen floor; data from wk 30, 32, and 34 are combined.
DISCUSSION
The frequency of floor laying decreased with time
and was affected by nest box availability, but not nest
box enclosure. Ducks with more than 6 wk of laying
experience were consistent in their selection of nest site
within and across weeks, and most laid their eggs within nest boxes. Most floor eggs were laid during the time
period of high nest activity.
Young commercial breeder duck hens are reported
to lay 30 to 40% of their eggs on the pen floor (Cherry
and Morris, 2008), and although the proportion of floor
laying decreases with flock age, it rarely falls below
13% (D. J. Shafer, Woodland Farms, Los Angeles, CA,
personal communication). In this study, floor laying followed a similar trend. It was highest at the start of
the laying period, decreased as egg production rate increased, and leveled off at 25 and 10% in pens with ratios of 4 ducks/box and 1 duck/box, respectively, when
the ducks reached 29 wk of age. Similar results have
also been reported in studies of nest site selection by
commercial chickens. For chickens, the high incidence
of floor eggs near the beginning of the laying period has
been attributed to the tendency of most young hens to
floor lay before establishing stable nest choices (Kite
et al., 1980; Rietveld-Piepers et al., 1985), whereas the
later plateau in the proportion of floor eggs has been
proposed to reflect the behavior of a subset of hens
classified as consistent floor layers (Kite et al., 1980).
It was not possible to assess the individual laying patterns of the study ducks before 30 wk of age. However,
the first egg to be laid in 14 of the 16 pens was laid
on the floor, lending some support to the notion that
early floor-laying activity may reflect the behavior of
inexperienced layers.
Of the 55% of ducks older than 30 wk of age that laid
eggs in nest boxes as well as on the pen floor, only 5%
laid more than 70% of their eggs on the floor and could
therefore be described as floor layers. Overall, ducks
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could not be categorized as either floor or nest layers,
which indicates that the plateau in the number of floor
eggs observed after wk 29 of age was not caused by the
behavior of just a subset of consistently floor-laying
ducks. The majority of ducks laid most of their eggs
within nest boxes, and floor laid only occasionally. It is
unclear whether these instances of occasional floor laying reflected the ducks’ choices to lay in a new location
or their inability to secure a nest box. However, the fact
that average weekly laying location consistency was
significantly higher, and floor laying was significantly
lower, among ducks housed in pens with 4 ducks/box
vs. 1 duck/box provides some support for the latter.
Ducks laid more floor eggs when housed in pens with
4 ducks/box (the duck per box ratio typically used by
the duck industry), than in pens with 1 duck/box. Accounting for changes in available floor space caused by
the placement of an additional 6 nest boxes in the same
pen area did not change this result, indicating that the
difference in floor laying frequency was caused by the
change in nest box availability. Still, the uneven distribution of eggs among the nest boxes suggested that
nest box competition may only partially account for
the floor laying behavior. Although typically at least
one duck entered each of the available nest boxes (Makagon, 2010), not all of the boxes contained eggs on any
given day. For example, when 2 nest boxes were available (4 ducks/box treatment group), often (on 38% of
the days) only 1 of them contained eggs. In pens with
1 duck/box, eggs were typically found in only 2 or 3 of
the 8 boxes. The particular nest boxes in which eggs
were laid were not consistent over time, suggesting that
nest box position within the pen did not play a primary
role in the ducks’ choice of laying location. Individually
housed Pekin ducks prefer to lay in nest boxes that
contain an egg (Makagon et al., 2011). The clumped
distributions of eggs laid by ducks in the current study
may therefore also reflect this preference.
Nest box concealment affects the nest choices of individually housed Pekin ducks. When they are able to
choose among box designs varying in level of enclosure,
individually housed ducks show a clear preference for
laying in nest boxes offering the highest degrees of enclosure (Makagon et al., 2011). One implication of these
results is that ducks might be more attracted to lay in
CL rather than OP boxes and that, as a result, floor
laying could be decreased by providing ducks with CL
boxes. However, this effect was not observed in the current study. It is possible that ducks find both OP and
CL boxes acceptable when they are not given a choice.
Alternately, individually and group-housed ducks may
use different criteria for evaluating the quality of potential nest sites. For example, individually housed ducks
may seek concealment, whereas group-housed ducks
may rely more strongly on more direct social cues, such
as the presence of conspecifics. The clumped distribution of eggs laid by group-housed ducks may reflect the
use of such social cues in nest site selection. Although
it was not directly assessed as part of this study, the
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Makagon and Mench
presence of conspecifics themselves may also influence
nest choice by Pekin ducks (Makagon, 2010).
In conclusion, understanding factors governing nest
site selection is an important step toward alleviating
the floor-laying problem that commonly occurs in commercial duck production. This study evaluated the
variation in floor-laying patterns among Pekin ducks,
and the effects of nest box availability and enclosure
on the frequency of floor laying. Although individual
ducks could not be classified as floor vs. nest users,
they did vary in their tendencies to floor lay. Although
none of the ducks floor laid exclusively, most did so
least occasionally. Increasing nest box availability by
providing each duck with a nest box decreased floor
laying. This 1 duck/box ratio is not feasible under commercial conditions. However, daily patterns of nest use
suggest that such a low duck-to-box ratio may not be
necessary, because eggs were typically found in only 3
of the 8 available nest boxes in the 1 duck/box treatment group. This suggests that optimizing the duck-tobox ratio without altering the degree of nest enclosure
could potentially decrease floor laying.
ACKNOWLEDGMENTS
We gratefully acknowledge Woodland Farms (Los
Angeles, CA) for generously donating the ducks, drinker lines, and feed for this project, and particularly
Brian Lee, Tom Bocianski, Cesar Chavez, and Daniel
Shafer of Woodland Farms for sharing their expertise.
We thank Ed DePeters at the University of California, Davis, for allowing us use of his laboratory space
to boil eggs, and Amanda Grout, Stephanie Robles,
Cassandra Tucker, members of the Mench Laboratory
and the Tucker Laboratory at the University of California, Davis, and our dedicated interns at the University
of California, Davis, especially Nataya Chayasriwong,
Ruby Hsieh, Kacie Minamide, Ricarda Roberto, Felicia
Tam and Alyson Yamaguchi, for their participation in
various phases of the project.
REFERENCES
Appleby, M. C., and H. E. McRae. 1983. A method for identifying
eggs laid by individual birds. Behav. Res. Methods Instrum.
15:399–400.
Bjarvall, A. 1970. Nest-site selection by the mallard (Anas platyrhynchos). A questionnaire with special reference to the significance of artificial nests. Viltrevy (Stockh.) 7:151–179.
Cherry, P., and T. R. Morris. 2008. Domestic Duck Production: Science and Practice. CABI, Wallingford, Oxford, UK.
Federation of Animal Science Societies (FASS). 1999. Guide for the
Care and Use of Agricultural Animals in Agricultural Research
and Teaching. 1st rev. ed. FASS, Savoy, IL.
Kite, V. G., R. B. Cumming, and M. Wodzicka-Tomaszewska. 1980.
Nesting behaviour of hens in relation to the problem of floor eggs.
Pages 93–96 in Proc. IV Rev. Rural Sci. Univ. New England,
Armidale, New South Wales, Australia.
Makagon, M. M. 2010. Nest site selection by Pekin ducks. PhD Diss.
Univ. California, Davis.
Makagon, M. M., C. B. Tucker, and J. A. Mench. 2011. Factors
affecting nest choice by Pekin ducks. Appl. Anim. Behav. Sci.
129:121–128.
Riddle, O. 1910. Studies with Sudan III in metabolism and inheritance. J. Exp. Zool. 8:163–184.
Rietveld-Piepers, B., H. J. Blokhuis, and P. R. Wiepkema. 1985.
Egg–laying behaviour and nest-site selection of domestic hens
kept in small floor-pens. Appl. Anim. Behav. Sci. 14:75–88.
Sherwin, C. M., and C. J. Nicol. 1992. Behaviour and production
of laying hens in three prototypes of cages incorporating nests.
Appl. Anim. Behav. Sci. 35:41–54.