Measuring Pin Bones in Hens - A Step by Step Guide

This guide will walk you through how to measure pin bones accurately and what the results might mean in relation to whether your in is likely to be ovulating or not.

It can be difficult in small flocks of pet hens to know which hens are laying, particularly in winter months when possibly three eggs may be laid by a flock of say four or five hens (depending on breed). Some hens will consistently lay earlier in the morning and others later. This pattern of earlier or later laying is often maintained from winter to summer, but the time of lay in the winter can be later in the morning. Some hens may not lay in the nest box, particularly if they lay after the hen coop doors are open. Hens can often be seen returning to the coop to lay in the nest box after ranging but some hens will find a more local nesting area, such as in hay stores on equestrian establishments. These eggs are often then found at a much later time, unless the alternative laying site is known.

If a hen becomes broody, she is often seen in the nest box and can often be assumed to be laying. Sometimes hens suffering with salpingitis (infected oviducts) can be regularly seen in the nest area. Neither of these types of hen are likely to be laying.

One way to check if a hen is laying is to try to feel a developing egg. This is best performed late at night either by abdominal palpation or an internal examination via the cloaca. Avoid feeling in the afternoon when the egg will be in a soft-shelled state and can be damaged more easily.

A safer method, which can be performed at any time of the day is to assess the distance between the pin bones of the pelvis.

Both of these techniques can risk damaging the egg or harming the bird so you must be gentle.

What Are Pin Bones and Why Measure Them?

Pin bones are the two small bones located on either side of a hen’s vent, part of the pelvis. They are important because their spacing changes depending on the hen’s body condition and reproductive status. When a hen is healthy and ready to lay eggs, the pin bones tend to spread apart to allow eggs to pass through easily.

Step-by-Step Guide to Measuring Pin Bones

Step 1: Prepare Your Hen

Choose a quiet time when your hen is calm. Approach her gently and hold her securely but softly. If your hen is nervous, take a few moments to soothe her before starting.

Step 2: Locate the Pin Bones

Feel gently around the vent area, below the tail. The pin bones are located on either side of the vent. You can feel them as two small, firm points.

Step 3: Measure the Distance Between Pin Bones

Use your fingers to gently feel how wide the gap is between the pin bones apart without trying to move the bones or inserting your fingers into the vent. This is all felt from outside the bird. Feel how many of your fingers can fit in between and compare that to the expected size of egg your hen lays.

Step 4: Assess the Measurement

When a bird is in lay, she should have a gap between her pin bones at a similar width to size of egg she is expected to lay. Bantams will lay smaller eggs and have smaller widths, approximately 1-1.5 fingers width. Commercial hybrid hens will lay larger eggs and usually be 2-3 fingers in width. Large traditional breeds will be even larger. This is a good, non-invasive way to check status of lay and can be performed every few days to observe any changes.

When to Seek Veterinary Advice

If your hen’s pin bone measurements do not match what you are seeing in the nest box, or they are not laying when they should be in season, seek veterinary attention.