Data from: Eviction-driven infanticide and sexually selected adoption and infanticide in a neotropical parrot
Data files
May 09, 2024 version files 71.30 KB
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Infanticide_popsize.csv
1.11 KB
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Mateloss_infanticide.csv
50.20 KB
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README.md
9.84 KB
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Rep_male_fitness.csv
10.15 KB
Abstract
Infanticide and adoption have been attributed to sexual selection, where an individual later reproduces with the parent whose offspring it killed or adopted. While sexually-selected infanticide is well known, evidence for sexually-selected adoption is anecdotal. We report on both behaviors at 346 nests over 27 years in green-rumped parrotlets (Forpus passerinus) in Venezuela. Parrotlets are monogamous with long-term pairbonds, exhibit a strongly male-biased adult sex ratio, and nest in cavities that are in short supply, creating intense competition for nest sites and mates. Infanticide attacks occurred at 256 nests in two distinct contexts: (1) Attacks were primarily committed by nonbreeding pairs (69%) attempting to evict parents from the cavity. Infanticide attacks per nest were positively correlated with population size and evicting pairs never adopted abandoned offspring. Competition for limited nest sites was a primary cause of eviction-driven infanticide; and (2) Attacks occurred less frequently at nests where one mate died (31%), was perpetrated primarily by stepparents of both sexes, and was independent of population size. Thus, within a single species and mating system, infanticide occurred in multiple contexts due to multiple drivers. Nevertheless, 48% of stepparents of both sexes adopted offspring, and another 23% of stepfathers exhibited both infanticide and long-term care. Stepfathers were often young males who subsequently nested with widows, reaching earlier ages of first breeding than competitors and demonstrating sexually-selected adoption. Adoption and infanticide conferred similar fitness benefits to stepfathers and appeared to be equivalent strategies driven by limited breeding opportunities, male-biased sex ratios and long-term monogamy.
README: Data from: Eviction-driven infanticide and sexually selected adoption and infanticide in a neotropical parrot
https://doi.org/10.5061/dryad.h70rxwds4
Data sets include:
1. Mateloss_infanticide.csv
2. Infanticide_popsize_csv
3. Rep_male_fitness.csv
Description of the data and file structure
Data for infanticide attacks and mate loss events at nests of the green-rumped parrotlet (Forpus passerinus) (#1 above), number of attacks annually (#2 above), and fitness of stepfathers (replacement males) at nests with widows (#3 above).
DATA-SPECIFIC INFORMATION FOR: Mateloss_infanticide.csv
1. Number of Variables: 50
2. Number of Cases: 346
3. Variable List:
Nest : nest identifier composed of year (first two digits), nest type (1 field, B = box, N = natural), number (identifies the box or natural nest, 1-3 fields), and attempt in the nest (A, B, etc.; 1 field)
Year: year of the nesting attempt
Mateloss: Did one of the parents die after the first egg was laid? TRUE if occurred, FALSE if did not occur
Contest: Was there an obvious commotion at nest boxes from contests among competing parrotlets that alerted us to the death of a parent? TRUE if occurred, FALSE if did not occur
Takeover: Did another pair take possession of the nest site? TRUE if occurred, FALSE if did not occur
Infancid: Did infanticide occur? TRUE if occurred, FALSE if did not occur
Abandon: Whether a nest was abandoned by parents: NO = not abandoned; BEFORE = abandoned before the nest was attacked; AFTER = abandoned after the nest was attacked; blank = not applicable or not abandoned.
Femid: identity of the nesting female parent
Femdeath: NO, DD = Definitely Dead, Death Suspected (later confirmed)
Malid: identity of the nesting male parent
Maldeath: NO, DD = Definitely Dead, Death Suspected (later confirmed)
Femrep: identity of the replacement female (stepmother)
Frepstat: NF = Neighboring female, LF = Lone Female, MF = member of male-female pair
Malrep : identity for the replacement male (stepfather)
Mrepstat: LM = Lone Male, MF = member of male-female pair, MM = member of male-male pair
Killer1: identity of the attacking individual. Blank if not known
Killsex1: sex of the attacking individual. Blank if not known
Killcon1: KD = killer definitely observed, KS = killer suspected based on behavior and proximity to the nest. Blank if not known
K1stat: the status of killer 1. RM = replacement male (stepfather), MF = member of male-female pair, LM = lone male, MM = member of male-male pair. Blank if not known
Killer2: identity of the second attacking individual. Blank if not known
Killsex2: sex of the additional attacking individual. Blank if not known
Killcon2: KD = second killer definitely observed, KS = second killer suspected based on behavior and proximity. Blank if not known
K2stat: (status of killer 2) RM = replacement male (stepfather), MF = member of male-female pair, LM = lone male, MM = member of male-male pair. Blank if not known
Maxflock: Maximum number of birds (excluding original nesting pair) observed on one occasion in the vicinity of the nest during an event.
No_LM: Number of birds in Maxflock that were lone males
No_NM: Number of males in Maxflock that were from neighboring nests
No_LF: Number of birds in Maxflock that were lone females
No_NF: Number of females in Maxflock that were from neighboring nests
No_MF: Number of male-female pairs in Maxflock
No_NP: Number of male-female pairs in Maxflock that were from a neighboring nest
Stardate: Starting date of event (month/day/year)
Starcon: confidence in the start date to an accuracy of ñ2 or 3 days? Y=yes, N=no.
Killdate: First date that eggs or nestlings were attacked by other parrotlets (mm/dd/year).
Flkstar: First date that a pair or a flock of parrotlets was sighted at the nestbox contesting a mate loss or harassing a breeding pair.
Flkend: Last date that a pair or a flock of parrotlets was sighted at the nest box
When: Stage of the nest when the event occurred. PRO=Prospecting or pair formation prior to clutch initiation, LAY=during egg laying, INC=incubation, HAT=hatching, BRD=brooding, BRF= brooding to start of fledging, FLD=fledging
Eggs: Number of eggs in nest at time of event
Chicks: Number of nestlings in nest at time of event
EggAtt: Number of eggs attacked (always destroyed if attacked)
YgAtt: Number of nestlings attacked
YgKill: Number of nestlings killed by the attack
YgFail: Number of young that were attacked but subsequently died due to other causes including predation, starvation etc.
YgFled: Number of young that were attacked but successfully fledged anyway
NstWatch: Were the observations collected during a regularly scheduled nestwatch? Y=yes, N=no
Nowatch: Number of nest watches that were conducted
HrWatch: Total hours that the box was observed during all nest watches.
Failed: Did the nest fail? N = no, Y = yes
FailStage: stage when failed: 1= egg laying before full clutch; 2=during incubation after full clutch; 3=during hatching; 4=during brooding (female still with young); 5= after brooding but before fledging; 6=during fledging
Reason: Cause of nest failure: 1=mate loss; 4=harassment from nearby nesting neighbor during or before egg-laying; 5=predation; 6=nest abandoned, reason unknown; 7=intraspecific harassment by other pairs, male-male pairs, and mobs; 8=miscellaneous reasons (disease, hypothermia, no apparent cause), 11=infanticide on eggs or nestlings.
Fledge: Number of young fledging from the nest
DATA-SPECIFIC INFORMATION FOR: Infanticide_popsize.csv
1. Number of Variables: 9
2. Number of Cases: 27
3. Variable List:
Year: year of study
Infant_yr: number of infanticide attacks
Infant_mateloss_yr: number of infanticide attacks at nests where a parent died
Infant_intactpr_yr: number of infanticide attacks at nests with intact pairs
Tot_no_nests: number of nests
Infant_pernest: infanticide attacks per nest
Infant_mateloss_pernest: infanticide attacks per nest experiencing death of a parent
Infant_intact_pernest: infanticide attacks per nest with intact pairs
Tot_adults: total number of banded adults detected each year
DATA-SPECIFIC INFORMATION FOR: Rep_Male_Fitness_archive.csv
1. Number of Variables: 28
2. Number of Cases: 101
3. Variable List:
Nest: nest identifier composed of year (first two digits), nest type (1 field, B = box, N = natural), number (identifies the box or natural nest, 1-3 fields), and attempt in the nest (A, B, etc.; 1 field)
Femid: identity of the nesting female parent
Malrep : identity for the replacement male (stepfather)
Mateloss: Did one of the parents die after the first egg was laid? TRUE if occurred, FALSE if did not occur
Takeover: Did another pair take possession of the nest site? TRUE if occurred, FALSE if did not occur
Infancid: Did infanticide occur? TRUE if occurred, FALSE if did not occur
Young_Fledged: the future number of offspring produced together at subsequent nests by the widow and stepfather.
Numb_FullClutch: the future number of clutches produced together at subsequent nests by the widow and stepfather.
NestTogeth: Did the widow and stepfather nest together in the future? NO, YES
BdAs: Was the stepfather banded as an adult (A) or nestling (N). Blanks indicate identify of stepfather was not fully known (unbanded, partially banded, unknown).
Year_band: year when the stepfather was banded
Age_RepMale: Age in years of the stepfather if banded as a nestling. If banded as an adult, indicates years prior to (positive number), during (0), or after (negative number) after the current nesting attempt when the stepfather was banded.
Repenter: Was the stepfather observed to enter the nest box during nest watches? Y = yes, N = No, U = Unknown
HrWatch: Number of hours that the nest was observed during nest watches
Killer1: identity of the attacking individual. Blank if not known
Killcon1: KD = killer definitely observed, KS = killer suspected based on behavior and proximity to the nest, Blank if not known
K1stat: the status of killer 1. RM = replacement male (stepfather), MF = member of male-female pair, LM = lone male, MM = member of male-male pair. Blank if not known
Killer2: identity of the second attacking individual. Blank if not known
K2stat: (status of killer 2) RM = replacement male (stepfather), MF = member of male-female pair, LM = lone male, MM = member of male-male pair. Blank if not known
Killcon2: KD = second killer definitely observed, KS = second killer suspected based on behavior and proximity. Blank if not known
Next_Nest_Date: serial date of the next nest by the widow and stepfather given as the number of full days since midnight January 1, 1900
Egg1_STD: date of laying of the first egg of the current nesting attempt centered and standardized by one standard deviation within years (0 = mean date, negative values are earlier, positive values are later).
Egg1date: serial date of the current nest given as the number of full days since midnight January 1, 1900
Days2NextNest: Number of days from the termination of the current attempt (failure or fledging of the last young) until the first egg was laid at the next nesting attempt.
Fem_Next_Nest: nest box used by the widow for her next nesting attempt. Blank if there was no future attempt.
MateLoss_box: box number of the current nesting attempt extracted from the first variable.
Fem_NextNest_box: box number of the current nesting attempt extracted from Fem_Next_Nest
Nestnest_same_box: Was the next nest in the same box as the current nesting attempt? Yes, No, or NA (not applicable if there was no nesting attempt or the attempt was not with the stepfather)
Methods
We studied green-rumped parrotlets from 1988-2015 at Hato Masaguaral (8º34' N, 67º35' W), a working cattle ranch 45 km south of Calabozo in the state of Guárico, Venezuela. In 1988 and 1989, 106 identical nest boxes made of 1-m deep polyvinyl chloride tubes with hardware cloth interiors were installed along fence lines in a 4 km2 study area. We monitored an additional 20 nest boxes in some years in a third population 2.5 km from the others. Across the 27-year period of this study (1989-2015), a team of 2-5 field researchers annually monitored the fate of all nesting attempts in boxes. We captured 1512 breeding and nonbreeding adults with mist nets. They were banded with individually identifiable color bands and a numbered metal band, as were all nestlings (n = 7346).
Nest boxes were visited daily every 1-3 days throughout the entire nesting season to determine nest contents and the identities of adults in the vicinity. Data collected from these checks, combined with 2,140 hours of nest watches and video recording in nests, provide strong evidence for the occurrence of infanticide and mate loss as well as adoption and nest abandonment. Parrotlets are unable to remove items from their meter-deep nest box because they use their bill and legs to ascend the nest cavity. Thus, nestlings or eggs killed by infanticide, or that died from other causes like starvation, remained in the nest box where we examined them during routine nest checks. Nestlings attacked by parrotlets usually exhibited bruising to the head, but also to the neck, back, wings and/or legs, with visible internal hemorrhaging and external lacerations.
The obvious commotion at nest boxes from contests among parrotlets alerted us to the death of a parent (which was confirmed by resighting efforts during the current and subsequent years) and attempts to evict breeding pairs from nests. These nests were often watched for periods of 1-3 hours to identify the individuals present, note their social status, and record their behaviors, and thereafter were revisited regularly to determine the fate of the nest and the identity of the attending birds. Social status was classified as actively nesting male-female pairs, nonbreeding male-female pairs, unpaired males, and male-male pairs.
We classified stepparents as adopting unrelated offspring if no offspring mortality or injuries occurred from infanticide attacks, and stepparents exhibited forms of parental care, ranging from feeding of offspring to tolerance. Daily nest checks and periodic nest watches (765 hours at 95 nests) and video monitoring (325 hours at 4 nests) allowed us to observe whether stepparents exhibited adoption behaviors, and to determine whether parents abandoned the remaining eggs and/or nestlings before or after an infanticide or mate loss event. Nest watches and subsequent daily visits to the box determined whether stepparents entered the nest box or were prevented from doing so by the surviving parent, fed their new mates outside of the box, and participated with the widowed parent in defending the box from other parrotlets. Nests were classified as abandoned when multiple visits over several days determined that nestlings had not been fed (i.e., had empty crops and symptoms of dehydration or malnourishment), eggs were not incubated (i.e., were cold, unattended, or buried in the bottom of the box), parents and stepparents were not nearby, and other parrotlets were prospecting at the box or entering it.