DOI: 10.5061/dryad.k98sf7mgz
title: Dates and numbers of migratory return of territorial and non-territorial male and female Wilson's Warblers

description: Early migratory return for territorial passerines is important, since
 earlier return results in better territories, and greater reproductive
 success.  Many passerine studies have found that migratory return
 dates for first-breeding-season (SY) individuals was a week or less later
 than for older (ASY) birds. Many of both ASY and SY birds in these studies
 became territorial, although more SY than ASY birds became non-territorial
 floaters.  In this study of Wilson’s Warblers, however, nearly
 all individuals returning early and becoming territorial  were
 ASY birds, and very few were SY birds.  However, second waves of
 returning Wilson’s Warblers, containing both SY and ASY birds, returned
 about three to five weeks after the first migratory waves, and no males in
 these second waves ever became territorial.  No later-returning,
 second-wave female initially ever became territorial either, although some
 subsequently became replacement mates for earlier-returning
 males.  Some male Wilson’s Warblers were territorial, and others
 were non-territorial, during all of their study-area years. 
 However, some males switched status over successive years, and migratory
 return when non-territorial, always was several weeks later than when
 territorial.  Findings from this study indicated that, for some
 males during some years, non-territoriality was more adaptive than was
 territoriality.  This study’s finding, of three-to-five-week
 later migratory return waves for non-territorial, than for territorial,
 Wilson’s Warblers, supports findings by Stewart (1973), that Wilson’s
 Warblers return to breeding grounds in two migratory waves. 
 Findings from both studies may provide empirical evidence supporting
 Kokko’s (1999) hypothesis, that migratory birds not competing for
 territories should return to breeding grounds later, on their
 “cost-minimizing dates.” 
description: Data collected through 13 years of daily observations in the
 study area during Wilson's Warbler breeding seasons.
description: # Dates and numbers of migratory return of territorial and non-territorial
 male and female Wilson's Warblers ## Brief summary of
 dataset The basic purpose of the paper, of all graphs and tables, and thus
 of all data files, is to compare the migratory arrival of territorial
 versus non-territorial Wilson's Warblers. ## Description of the data
 and file structure This dataset contains six data files, used to formulate
 all graphs and two of four tables in the paper. All DRYAD data files have
 the same structure, that is, four columns, A, B, C, and D, and the same
 number of rows, 1 to 60. **Column A** gives the date of observations.
 **Column B** gives the order of those dates, that is, the first date on
 which relevant observations were made was 11 March, and this is ordered
 #1. Twelve March is ordered #2, etc. Nine May is ordered lastly at #60.
 **Column C** states the number of territorial Wilson's Warblers seen
 on the date stated in column A. **Column D** states the number of
 non-territorial Wilson's Warblers seen on the date stated in column
 A. While all data files have this same structure, they differ in specifics
 of the recorded data, such as migratory arrival dates, whether data was
 for males or females, the number of birds that were considered, and/or
 whether birds were banded or unbanded. For example, data file #2 shows
 total numbers of territorial females that were recorded arriving between
 15 March through 28 April, and total numbers of non-territorial females
 that were recorded between 14 April and 9 May. However, data file #4
 considers only five territorial males arriving between 11 and 21 March,
 and five non-territorial males arriving between 6 and 25 April. Although
 actual sightings of Wilson's Warblers on specific dates were
 relevant, the numbers sighted on other dates always were listed, whether
 any birds were seen or not. In other words, many dates in the files
 recorded zero sightings. No dates in the data files were left blank, and
 there was no missing data. Specifics **DATA FILES 1 AND 2** I used data
 files 1 and 2 to produce Graphs (Figs.) 3a and 3b in the paper, which are
 plots of migratory arrival for territorial and non-territorial
 Wilson's Warbler males and females respectively. I also used data
 files 1 and 2, with slight adjustments explained in METHODS, to determined
 the mean dates of migratory arrival stated in Tables 1a and 1b, which give
 the mean migratory arrival dates respectively for male and female
 Wilson's Warblers. In data files 1 and 2 I state the dates that I saw
 respective numbers of male and female Orange-crowned Warblers during each
 day, cumulative for all study years, from 1997 through 2010, excluding
 year 2000, starting on 11 March and ending on 9 May. The purposes of
 graphs (Figs.) 3a and 3b, and of Tables 1a and 1b, and thus the purposes
 of data files 1 and 2, are to compare the migratory arrival dates of
 territorial and non-territorial Wilson's Warblers. Data file #1, used
 for plotting male arrival in Fig. 3a, and for calculating mean male
 migratory arrival dates in Table 1a, shows that newly-arriving territorial
 male Wilson's Warrblers were sighted from 11 March through 16 April.
 Newly-arriving Non-territorial males were sighted starting on 5 April, and
 the last non-territorial male was assumed to have arrived on 9 May. The
 reason the exact final date for non-territorial arrival could not be
 determined, and had to be approximated, is that non-territorial males and
 females did not establish breeding territories, and establishment of
 breeding territories was the basis of determining arrival times for
 territorials. The basis for estimating the final arrival times for
 non-territorial males and females is explained in the paper's
 METHODS. Data file #2, used for plotting female Wilson's Warbler
 arrival in Fig. 3b, and for calculating mean migratory arrival dates in
 Table 1b, shows that Newly-arriving territorial female orange-crowned
 Warrblers were sighted from 15 March through 28 April. Non-territorial
 females were sighted starting on 14 April, and the last non-territorial
 female was assumed to have arrived on 9 May. IMPORTANTLY, DATA FILES 1 AND
 2 SHOW A SECOND COLUMN, FOLLOWING THE DATE COLUMN, TITLED DAY. THIS COLUMN
 STATES THE ORDER OF THE DATES OF MIGRATORY ARRIVAL. (e.g., 11 March is #1
 in the order, and 9 May is #60, and last, in the order.). I USED THESE
 ORDER NUMBERS, RATHER THAN THE CALENDAR DATES AS SUCH, FOR PLOTTING THE
 GRAPHS IN FIGS. 3A AND 3B, AND FOR CALCULATION OF MEAN VALUES IN TABLES 1A
 AND 1B. **DATA FILES 3 AND 4** I used data files 3 and 4 to produce graphs
 (Figs.) 3c and 3d respectively. The purposes of graphs 3c and 3d, and thus
 the purposes of data files 3 and 4, were to compare the migratory arrival
 dates of unbanded non-territorial male and female Wilson's Warblers
 respectively with the arrival dates of color-banded non-territorial male
 and female Wilson's Warblers. These plots indicate, through
 inspection, whether or not unbanded non-territorial males (Fig. 3c) and
 females (Fig. 3d), identified based on their behaviors, had similar
 migratory arrival profiles as did non-territorial males and females
 identified based on color-banded greater certainty. Data file # 3 shows
 that unbanded non-territorial males arrived from migration between 11
 April and 9 May, and color-banded non-territorial males similarly arrived
 between 14 April and 9 May. Data file #4 shows that unbanded
 non-territorial females arrived between 11 April and 9 May, and
 color-banded non-territorial females similarly arrived between 5 April and
 9 May. As was the case for Figs. 3a and 3b, I used the numerical order of
 arrival dates in the data files to plot Figs. 3c and 3d, rather than the
 calendar dates as such. **DATA FILES 5 AND 6** I used data files 5 and 6
 to produce Tables 1c and 1d respectively. Data from Table 1c incorporates
 male migratory arrival dates for the earliest five annually returning
 territorial male Wilson's Warblers, compared with the arrival dates
 for the earliest five annually returning non-territorial males. Data from
 Table 1d incorporates male migratory arrival dates for Wilson's
 Warbler males that alternatively were either territorial and
 non-territorial during respective years in the study area. The purposes of
 Tables 1c and 1d, and thus of data files 5 and 6, was to present two
 additional ways for determining the mean migratory return dates for
 territorial versus non-territorial male Wilson's Warblers. These two
 ways were additional to the mean dates presented for those two
 subpopulations of males determined in Table 1a . Data file #5 shows that
 the five earliest annually returning territorial males arrived between 11
 March and 21 March, while the five earliest-returning non-territorial
 males arrived considerably later, between 26 March and 25 April. Data file
 #6 incorporates male migratory arrival dates for males that alternatively
 were territorial and non-territorial during their tenures in the study
 area. Data file #6 shows that migratory arrival dates when males were
 territorial ranged between 21 March and 31 March, and when those same
 males were non-territorial ranged, considerably later, between 5 April and
 9 May. As was the case for data files 1, 2, 3, and 4, migratory return
 dates in data files 5 and 6 are listed from 11 March through 9 May, and
 the order of migratory return is indicated as being from 1 through 60.
 Again, the order of return, and not actual calendar dates, was used to
 calculate mean values. Links for sharing and code. - None