Field Notes Journal Entry
Towards a Breeding Typology
Not just when species are present, but how the year renews itself
From Presence to Renewal
In earlier entries in this series, I’ve been looking at how species move through the year — whether they are present or absent, constant or seasonal, and how those patterns emerge when observations are grouped by month.
Those analyses describe how species occupy the year.
But there is another pattern: not just when species are present, but when they are seen with young.
If the year can be described through repeated encounters, then some of those encounters carry a particular significance. They are moments when the next generation becomes visible.
That suggests a further question: If these observations are grouped in the same way, do they also fall into recognisable types?
A Simple Approach
The approach is the same as before, but applied to a more specific subset of the data.
For each species, observations in which dependent young were recorded are grouped by month. From these, two simple measures are derived:
- Total sightings with young — how many individuals were recorded
- Presence with young — on how many days such observations were made
From these short sequences, a small number of features can be calculated: how many months the signal appears in, how concentrated it is, where it is centred, and how it behaves after its peak.
As before, the aim is not to build a model, but to see whether the shapes already present in the data can be given names.
Patterns Begin to Emerge
When viewed across species, these breeding-related signals do begin to fall into recognisable forms.
A small typology emerges:
| Species | Breeding Classification |
|---|---|
| Great Tit | Moderate breeding window |
| Robin | Diffuse / ambiguous breeding signal |
| Mute Swan | Diffuse / ambiguous breeding signal |
| Common Starling | Moderate breeding window |
These categories are not defined in advance. They arise from the structure of the curves themselves.
Shapes of Breeding Activity
What is striking is how different these patterns can be.
Some species show a narrow, sharply defined window — a brief period in which young are encountered before dispersal. This produces a compact peak in late spring or early summer.
Others show a broader signal. The peak is still visible, but the activity is spread across several months, suggesting either repeated broods, staggered nesting, or a longer period in which young remain detectable.
And then there are species where the signal persists well beyond its peak. In these cases, the curve does not simply rise and fall. It rises, and then continues — a long tail extending through the summer and into the autumn.
This is not a longer breeding season in the strict sense, but something different: a prolonged period of association between parents and offspring.
From Shape to Category
From these observations, a small set of categories can be defined:
| Classification | Pattern |
|---|---|
| Brief breeding window | Narrow, sharply peaked signal with rapid decline |
| Moderate breeding window | Clear seasonal window of intermediate breadth |
| Extended family association | Broad signal with prolonged post-peak persistence |
| Diffuse / ambiguous signal | Present but irregular or not cleanly resolved |
| No breeding signal | Insufficient observations to define a pattern |
As with the seasonal classifier, the categories are descriptive rather than prescriptive. They do not impose structure on the data, but reflect patterns already visible in the underlying curves.
What These Patterns Represent
It is important to be clear about what is being captured here.
These classifications are not direct descriptions of breeding biology. They do not identify nesting dates, clutch sizes, or reproductive success.
They describe something more immediate:
The seasonal shape of observed breeding activity
A brief breeding window may reflect the period in which fledged young are visible before dispersal. An extended pattern may reflect the continued presence of dependent young alongside the adults.
In that sense, the patterns are shaped not only by biology, but by behaviour and detectability — just as with the seasonal classifications.
Patterns of Renewal
Seen alongside the seasonal types, these categories add a second dimension to the picture.
The seasonal classifier describes how species occupy the year. The breeding classifier describes how the year renews itself — when new individuals appear, and how long they remain visible.
Together, they begin to form a more complete account of the rhythms of the place.
Limitations and Observational Bias
The same limitations apply here as before, perhaps even more strongly.
Observations of dependent young are less frequent and more uneven than general sightings. Some species are easy to recognise in family groups. Others are not. Some remain visible for long periods; others disperse quickly.
As a result, the classifications reflect not just biological patterns, but patterns of encounter.
A species classified as having an extended breeding signal may not breed for longer than others, but may simply keep its young visible for longer. A species with a brief window may be equally successful, but less often observed in that phase.
These are not errors, but part of what is being described.
What This Adds
The method remains simple. The rules are transparent. The categories are few.
But the effect is to shift the perspective slightly.
From a record of what is present, and when, to something more dynamic: a record of when the next generation appears, and how that presence unfolds across the months.
Looking Ahead
It will be interesting to see how robust these categories prove to be as more species are added.
Whether additional types emerge, whether the boundaries shift, or whether some patterns prove harder to classify than others.
For now, though, the approach offers a second way of reading the data.
Not just as a record of presence, but as a set of recurring patterns of renewal — moments in the year when the familiar landscape briefly contains something new.