Marked Birds Database concept – bird ages

One of the main aspects of a bird that I like to track in the Marked Birds Database is the age of a bird at all stages of its life.

In this article I explain how bird ages are handled.

View the video that accompanies this article:

Bird ages

The database keeps track of three different ages:

  1. The age of the bird at the time it was ringed
  2. The age of the bird at the time it was observed
  3. The age of the bird today (known in the system as the ‘Current Age’)

Age at the time of ringing

You get this age from the ringer or ringing station when you receive the ringing details.

Once received, it can potentially update all observation ages and the Current Age.

Age at the time it was observed

When first observing the bird, this is the only age of the bird that you have and is typically determined by yourself in the field.

Once you have received the ringing details you will know the exact age at the time you observed it and this may or may not be the same age as you determined at the time.

Once an age for a bird is added, the observation age is automatically filled in each time you create a new observation for that bird.

Current Age

The Current Age is the age of the bird today. It will therefore change each year.

When first observing the bird, the Current Age will be the same as the observation age because this is the only age you have for the bird.

Each calendar year though, the Current Age will be increased by one and once you have received the ringing details, the exact Current Age can be calculated.

All ages work together

Let’s consider a typical scenario:

1. First observation

You observe a bird in the field. It is an adult (for example older than 4th calendar year) but you don’t know it’s exact age. The ages will then be as follows:

  • Ringing age: unknown
  • Observation age: >4CY
  • Current Age: >4CY

2. Next observation

A few days pass by and you observe the bird again. You haven’t received the ringing details yet.

  • Ringing age: unknown
  • Observation age: >4CY (now automatically set)
  • Current Age: >4CY

3. Receiving the ringing details

You receive the ringing details and it turns out that the bird was ringed as a pullus 9 years ago (that’s 10 calendar years):

  • Ringing age: pullus
  • Observation age: >14CY (automatically adjusted)
  • Current Age: >14CY (automatically adjusted)

4. The next year

The first of January comes along meaning that the bird is now in its next calendar year. The Current Age can now be (automatically) increased by 1:

  • Ringing age: pullus
  • Observation age: >14CY
  • Current Age: >15CY

5. New observation

Fortunately, you observe the bird again. When creating the observation, the bird age is automatically set to the Current Age:

  • Ringing age: pullus
  • Observation age: >15CY
  • Current Age: >15CY

Summary

In short: the age of a bird at each stage is always available and once set, automatically calculated.

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