Estimation of the nestling age
and
calculating of the hatching date distribution
from the nestling age and observation dates


Description of the probability method of nestlings' ageing and its usage in the investigations into breeding phenology can be found in the papers:

Kania W. 1983. [Probability method of ageing Passerine nestlings and its usage in breeding phenology investigations of starling]. Notatki Ornitologiczne. 24: 46-68. In Polish. Figures, tables and summary in English.
(Download PDF file)

Kania W. 2001. [Age determination of the Great Tit Parus major nestlings by means of the probability method based on feather development]. Notatki Ornitologiczne. 42: 117-138. In Polish. Figures, tables and summary in English. (Download PDF file)

Kania W. 2004. Observer error in measurements of nestling wing length in small passerines. Ring 26, 2: 79-87 (Download PDF file)

To facilitate the preparation of the probability table converting trait value to nestling age as well as for determination of the hatching dates distribution in a population, two computer program packages were produced. They are described below and can be received for application in your own research.

Download file contab_hadate.zip, containing programs CONTAB and HADATE


General information on CONTAB and HADATE

The programs work in FoxPro for DOS and in DOS. They are compiled and available together with supplementary DBF files as packed ZIP file.

Conditions which should be met by the data to be processed are listed below. This information could be also called up during executing the programs. If necessary, additional information or warnings about possible mistakes in the data will be printed on the screen.

Files with one's own data can be prepared with any programs capable of producing DBF for DOS files. Structure of appropriate file EXEMP... .DBF for DOS should then be used (see below).

CONTAB - creates the table converting value of trait to nestling age (DBF file) from everyday measurements of the trait correlated with age.

Files CONTAB.EXE, EXEMP1.DBF and FOXDX260.ESL are required. EXEMP1.DBF together with EXEMP2a.DBF and EXEMP2b.DBF are exemplary input databases for testing the program when dealing with different data sets.

1. The input DBF file with nestling measurements has to include fields: D1, D2, ... Dn (numerical, with any number of decimal places) containing measurements for consecutive (1, 2, ... n) days of life of the oldest nestling.
    Each record is designed for one nest.
    The fields D1, D2, ... Dn should be filled with the measurements of the nestling biggest among siblings at the time of measuring, not necessarily the same one each day.
    If there is lack of measurements on a particular day, 0 or nothing should be filled in.
    The input database can include additional fields, e.g. for nest number or hatching date.
    If you would like to explore abilities of the program, execute it taking as an input the exemplary files: EXEMP1.DBF (wing length of small passerine nestlings measured with accuracy - 1 mm), EXEMP2a.DBF and EXEMP2b.DBF (dummy measurements with accuracy - 0,1).

2. The 1st day of life = last 24 hours before finding the first hatchling, assumed the nest was checked each 24 hours.

3. Measurements should be taken daily at the same time, though gaps are permitted.

4. The conversion table is based on the assumption of permanent growth of the nestling. Thus the program will stop on encountering the measurements of lower value than that of the preceding day and will ask for correction in the input database. A slow growth compared to the measurement unit, resulting in equal measurement values on consecutive days, will be accepted. Nevertheless if those values are bigger, compared to values from the preceding day, by more than one unit, a mistake of measuring or writing is highly probable. Program will accept such data but will also inform you that they are probably incorrect.

5. Field NESTS in output database contains numbers of nestlings (or nests, as each nestling represents different nest), measurements of which were used for defining the age distribution for each measurement unit.

6. Field AVDAY in output database contains mean consecutive number of day of life of a nestling for each value of trait. This means may be useful, e.g., when analyzing the differences between age estimations taken from the conversion tables based on measurements collected in different populations.

7. The last records of the output database should be deleted if they were based on insufficient number of nestlings.

8. If measuring of nestlings ready to escape from the nest some days before natural fledging is stopped, it can result in overrepresentation of slower growing nestlings in the proof, biasing the conversion table for biggest nestlings.


HADATE - creates DBF file(s) with sums of probabilities of hatching on the consecutive days of the breeding period. Two input DBF files are needed: (1) database with numerical trait of the age of nestlings biggest in the brood and with dates of the observation; (2) probability conversion table (converting trait to age, e.g. one prepared with the aid of CONTAB) as well as HADATE.EXE and FOX2D260.ESL.

1. The input data DBF file has to include the fields: DATE (type of expression: date) with date of measuring, ME (numerical, with any number of decimal places) with measurement (e.g. wing length) for the nestling with highest value of that measurement among nestmates. Each nest should be represented by 1 record. See exemplary files: EXEMP3.DBF (data from 2 populations) and EXEMP4 (with gaps in data and with measurements bigger than included in the exemplary conversion table EXEMP2b2.DBF, see below).

2. The program uses the table converting trait values to age, formatted as DBF file with numerical fields ME, DZ, P1, P2, ... Pn. It can be received with the aid of the program CONTAB. See exemplary conversion table EXEMP11.DBF or EXEMP2B2, created with CONTAB from EXEMP1.DBF or EXEMP2a.DBF respectively.

3. Output database(s) contain(s) fields: HATCHDATE with hatching date; PKL with probability of hatching on the day (expressed as % of all nests included in the input database or as a number of nests - as requested); DZ (optional) with numbers of days from the beginning of the year or from other date.


1.9.2005