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Golondrinas Database - Nests

The core data set coding data relevant to each nesting attempt, the identity of breeders, timing of laying, and basic information on reproductive success. These data to be collected on all nests each season.

For a general explanation of default variable codes, click here.

Variable Name

Description, definitions, values and examples

Research site identifier (e.g. ‘hillbank’)

Box identifier - unique within each site

Nest site locations, i.e. the spatial coordinates of the box, are the key observational unit, not the physical box per se, therefore, box numbers must be unique within a study site, and if a box is relocated it must be given a new box identification number. If a box is retired, the number is not reused.

Every BOXID must have a corresponding entry in the ‘Boxes’ database.


Number of the nesting attempt for this box, this year

An attempt is defined only if at least one egg is laid in the nest.

  • # = sequential number

Interpretation of multiple nesting attempts within one box is only reliable if it is known whether or not the nesting adults have changed. For this reason field notes about the age of adults, and identifying characteristics could be critical for coding the variable ‘newbird’ (see below).


Accuracy on the coding of ‘ATTEMPT’

  • 1 = high accuracy. Box monitored frequently and from beginning of the season
  • 2 = low accuracy. There could have been an unrecorded attempt

Whether or not the second (or third, etc.) nesting attempt was initiated by a different pair of breeders than in the previous attempt

  • this variable is only coded if ‘ATTEMPT’ >1
  • the code (4 characters) signifies whether or not either or both sexes are different, and the confidence in that assessment

Format: F__M__

The first and third characters are fixed. Each sex can get one of four possible values, as follows:

  • Y = that sex is different from the previous attempt
    requires positive information, e.g. banded birds, clearly distinguishing plumage characters, etc
  • P = that sex is probably different from the previous attempt i.e. there is some evidence indicating a change, but not enough to reach the standard of using ‘Y’
  • N = that sex is not different from the previous attempt
  • U = unknown

Indicates experimental group

This set of codes will expand over time, as new experiments are conceived and implemented. Standard codes will be used by all participants.

  • C = control, the default value
    [additional codes will be assigned as needed]

Band number of male bird for that nest attempt

  • -7 = default value for unbanded breeders
  • -9 = male at the nest is banded, but the number has not been confirmed through capture

Note: this field declared as type ‘text’ in order to be compatible with assigning dummy unique identifiers to chicks or unbanded adults for which link ability is necessary into other data sets. For example, if feeding data were gathered on such a nest, a unique but arbitrary band number would be assigned using the following convention of concatenating several other fields:

{siteID}+{boxID}+{4-digit year}+{attempt}+‘M’ (or ‘F’ for female breeders)


Band number of female bird for that nest attempt

  • -7 = default value for unbanded breeders
  • -9 = female at the nest is banded, but the number has not been confirmed through capture
    [see note under ‘BANDM’]

Date of first egg (mm/dd/yyyy)

If the nest is visited during laying, code LAYDATE by counting back from the number of eggs first observed (assuming no skips in laying). If the clutch is started and completed between checks, count back from the observation date one day for each egg in the clutch, then take the midpoint of the remaining interval to your last check as the estimated laydate.


Number of days between the visits bracketing LAYDATE

e.g. if the nest is checked on day x (0 eggs) and then checked again on day x+3, when 2 eggs are found in the nest, ‘LAYACC’ = 3, laydate=day x+2, with possible error in laydate of 1 day.

Clutch completion date. Date of last egg in clutch (mm/dd/yyyy)

Number of days between the visits bracketing COMPDATE

This code will be used to identify cases of skipped days during the laying sequence.


Number of eggs at clutch completion

  • # = clutch size
  • -8 = not applicable e.g. if human disruption appeared to cause abandonment of the nesting attempt
  • -9 = clutch size unknown. Use this code if more than 6 days elapsed between the estimated clutch completion date (‘COMPDATE’) and the next nest check

Number of individual eggs lost

Examples: If all eggs are lost at once, this variable would be equal to CLUTCH. If one egg was damaged during incubation, and 2 eggs did not hatch, this variable would be coded ‘1’ (unhatched eggs have their own variable).


Cause of individual egg loss

Each letter code is followed by a numeral to indicate the number of eggs lost to that cause e.g. ‘P2’ would indicate two eggs lost to predation. This order must be strictly maintained.

  • NL = no partial clutch losses, the default value
  • P = predation (only used when there is tangible evidence of a predator)
  • X = human caused
  • U = unknown
Date of hatching of first egg (mm/dd/yyyy)
Number of days between visits bracketing HATCHDAT

Number of chicks at hatch

  • # = initial brood size (‘0’ if nest failed before hatching)
  • -7 = some chicks hatched, but the number was not known
  • -8 = not applicable e.g. human induced failure
  • -9 = not known whether eggs hatched or not

Number of eggs that fail to hatch

Eggs remaining more than 3 days after the last chick hatches should be coded here.



Number of individual chicks lost between hatching and fledging

Examples: if two nestlings starve and the rest successfully fledge, this variable = ‘2’. If the entire brood is preyed upon, this variable = BROODSIZ.


Cause of individual chick loss

Each letter code is followed by a numeral to indicate the number of chicks lost to that cause e.g. ‘P2’ would indicate two chicks lost to predation. This order MUST be strictly maintained.

  • NL = no losses, the default value
  • P = predation (again, some tangible evidence of predation required)
  • X = human caused
  • S = starvation. Evidence of gradual deterioration in this or other chicks in the brood should be observed (e.g. small size relative to brood mates). Also, the carcass should be in the nest
  • U = cause unknown (e.g. chick dead in nest, but no previous or subsequent evidence of food stress)
Date of chick banding (mm/dd/yyyy)

Total number of chicks that fledge from that nest attempt

  • 0 = known to have failed naturally without young fledging
  • # = number of chicks fledging. (if less than hatchnum, then chikloss must be coded >0)
  • -7 = some chicks fledged, but number unknown
  • -8 = human caused failure. E.g. if the nest was compromised through experimental manipulation, or if the nest was abandoned following unusually long human activity at the nest during banding, etc
  • -9 = unknown if nest fledged any young or not

Overall outcome of the nesting attempt

  • FL = at least some chicks known to fledge
  • P = nest failed due to predation of the eggs or chicks
  • A = nest failed due to parent abandonment
  • X = human caused
Date of last chick fledging or last egg or chick dying (mm/dd/yyyy)
Number of days between visits bracketing FATEDATE

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